INTRODUCTION TO COMPUTER ENGINEERING

Introduction to Hardware Engineering
A Practical Study Guide
Module 2
Prepared by:AGABI FRIDAY
Computer Science and Engineering Department
This Study guide is organized into three Chapters:
Chapter One: Computer Hardware Identification
Chapter Two: Computer System Assembly
Chapter Three: Computer System Troubleshooting and Maintenance
Chapter One
Computer Hardware Identification
A computer system contains the following components/devices:
Tower or Desktop case
Motherboard
Processor
Memory
Graphics Card
Sound Card
Modem & NIC
Floppy Disk
Hard Disk
CD-ROM / DVD ROM
PC Speakers
Monitor
Optional Extras
CD-Writer
ZIP Drive
TV-Card
A desktop or tower case is required to hold all your components together. It is your personal preference on which one
you decide choose. The desktop or tower cases come two in form factor AT and ATX. Nearly all the cases made
nowadays are ATX as the motherboard manufacturers make majority of their motherboard in the ATX form.
ATX Tower Casing
Motherboard
A motherboard is a Printed Circuit Board (PCB) that connects your processor, memory and all your expansion cards
together to assemble a PC.
The processor
The processor also known as CPU (Central Processing Unit) is the brain of a computer.
Memory
Memory is the name given to silicon chips that stores volatile computer data. Volatile means that the contents of
memory will be lost if the power of the computer is switched off.
Graphics card
Graphics card provides display output to your monitor. Your graphic device will most likely come on your motherboard.
Sound card
If you require sound for your PC then you will need a sound card. Sound controllers also come with system board
nowadays.
Modem
Modem stands for Modulator Demodulator. It converts digital signals to analogue so that it can travel via your
telephone line, and vice-versa. A modem is an essential item if you are intending to connect your PC to the internet
using dial-up access. It is also on the board of most computers.
Ethernet Cards
Ethernet cards are usually purchased separately from a computer, although many computers (such as the Macintosh)
now include an option for a pre-installed Ethernet card.
FDD
You need a FDD to access floppy disks.
Hard disk drive
Hard disk drive stores all your data including operating system, applications, user files and documents.
CD-ROM drive
Nearly all operating systems and applications software comes on CD. It is therefore essential to have a CD-ROM drive
for installing your applications.
PC speakers
Monitors
CD Writer / DVD Writer
CD Writer / DVD Writer is a very good option for a backup device.
ZIP drive
If you need to transfer large files from one PC to another, you will find floppy disks quite useless due to their limited
storage capacity. A ZIP drive could be your answer as ZIP disks can store 100 or 250 MB depending on which model
you choose.
TV card
A TV card gives you the option of watching TV on your monitor.
Chapter Two
A STEP-BY-STEP GUIDE TO COMPUTER SYSTEM ASSEMBLY
If you are thinking of building your own PC, or need practical information about PC hardware or software, you have
come to the right place. With easy to follow step by step guide combined with many images even a beginner can build,
configure and setup their own PC.
This section gives you an opportunity to learn more about Personal Computer hardware and software. We provide
clear easy to follow step by step instructions on how to build your own PC, according to your own specification. By
building your own PC you get exactly what you need and can save yourself allot of money compared to buying a new
manufactured PC.
At the end of the guide you will have a fully functional PC that should hopefully meet your individual needs. We also
provide advice and instructions on installing a specific hardware, this can be useful if you already have a PC and want
to upgrade or add certain hardware.
The information is placed under appropriate category. The Hardware section provides information about all the
required PC hardware such as motherboard, CPU, memory etc. It provides guidance to help you decide which
hardware is suitable for your needs. Our illustrated step by step guide shows you how to assemble a PC from scratch.
The software section shows you how to setup a new hard disk using appropriate software, so it’s ready for installing an
operating system. Installation guide for Windows XP is provided so that your system is up and running quickly and
smoothly. If you encounter any problems the troubleshooting section should take care of things. So what are you
waiting for, start building a PC today.
Hardware Information
To build your PC from scratch you will need to purchase all the necessary hardware. The first thing you must consider
before you start to shop around for your PC hardware is the specification of the hardware. You should think about what
you are going to use your PC for, before buying fancy expensive hardware. Otherwise you will end up buying hardware
which offers advance features that may not be necessary for your needs and end up wasting your money. For
example, you may be using your PC for word-processing, spreadsheet and browsing the web. You would not gain
much benefit by purchasing an advance 3D graphics card or having a top of the range processor. A simple graphics
card and a mid-range processor will satisfy your needs.
Below is a list of all the hardware required to build your system except the obvious requirement, keyboard and mouse.
The purpose of each is hardware is explained along with some guidance to help you choose your hardware. Select the
required hardware for more information.
Tower or Desktop case
Motherboard
Processor
Memory
Graphics Card
Sound Card
Modem
Floppy Disk
Hard Disk
CD-ROM / DVD ROM
PC Speakers
Monitor
Optional Extras
CD-Writer
ZIP Drive
TV-Card
Desktop or Tower Case
A desktop or tower case is required to hold all your components together. It is your personal preference on which one you decide choose. The desktop
or tower cases come two in form factor AT and ATX. Nearly all the cases made nowadays are ATX as the motherboard manufacturers make majority of
their motherboard in the ATX form. All cases come with PSU (Power Supply Unit), space to mount your FDD, CD-ROM, HDD etc. The case that I would
be using for demonstration is an ATX Midi Tower case as shown below.
Motherboard
A motherboard is a Printed Circuit Board (PCB) that connects your processor, memory and all your expansion cards
together to assemble a PC. Most motherboards made nowadays are ATX. An ATX motherboard has the standard I/O
(Input/Output) connectors such as PS/2 ports, parallel ports, serial ports, etc, built onto the motherboard. Old AT
motherboard on the other hand uses I/O cards and cables which needs to be plugged into the motherboard, which gets
a bit untidy. AT motherboard requires AT keyboard and AT power supply. ATX motherboard fits into an ATX case and
comes with an ATX power supply. The following is a pictures of an ATX motherboard.
As you have seen from the enlarged image, the motherboard comes with various expansion card slots and connectors.
It comes with 3 different expansion slots, 1 AGP, 5 PCI and 1 ISA slot. The AGP (Accelerated Graphics Port) is where
you would connect and AGP graphics card. The PCI slots is where you would connect cards such as sound card,
modem, tv card etc. The ISA slot is quite an old type of bus which is handy if you got some old hardware such as an
old ISA modem or sound card. The other connectors includes the Intel socket 370 CPU connector, the DIMM slot for
SDRAM, IDE connector for connecting your HDD, CD-ROM or other IDE devices, and FDD connector.
The processor
The processor also known as CPU (Central Processing Unit) is the brain of a computer. The faster the processor, the faster it will execute
instructions and run your programs. The leading CPU manufactures are Intel and AMD. Whichever manufacturer you decide to choose you will
have to make sure that you purchase a compatible motherboard.
Before buying your CPU consider what the system is going to be used for. If you are going to use your system for word-processing, browsing
the web or other basic tasks, it may be sufficient for you to use an Intel Celeron or an AMD Duron processor, both of which are available at a
very competitive price.
If the system is going to be used for spreadsheet, databases, graphics and playing advance games then you should consider an Intel Pentium
4 / Pentium D or an AMD Athlon 64 / Athlon 64 X2 processor. Pentium D and Athlon 64 X2 are both Dual Core. Which means they have two
CPU in one Chip. They are also 64 Bit and will support the new Windows Vista Operating System. These processors are very fast and are
capable of handling most of your computing needs. For building our demonstration PC we will be using an Intel Pentium III 866Mhz Socket 370
processor, as shown on the following image.
Memory
he name given to silicon chips that stores volatile computer data. Volatile means that the contents of memory will be lost if the power of the
switched off. Memory stores some of your operating system and application data while it is being run. The more memory you have in your
more application you can run simultaneously and will provide an overall better system performance.
Memory comes in many form. The older system uses SDRAM, while the current system uses DDR-SDRAM (Double Data Rate Synchronous
Dynamic Random Access Memory). Depending on your CPU bus, you have to use SDRAM to match your CPU bus speed. For example, PIII
750 runs at the bus speed of 100Mhz therefore you need SDRAM that run at 100MHz, known as PC100 SDRAM. However if you are going to
use PIII 866 you will require PC133 SDRAM which runs at 133Mhz bus speed. You also have to make sure that your motherboard can support
these speeds. New generation of memories are currently out. Intel P4 use rambus memory known as RDRAM and the new AMD processors
use DDR2 SDRAM. Some of the well known memory manufactures are Crucial, Kingston and Samsung.
The following is an image of an PC133 SDRAM that will be used for our demonstration PC.
Graphics card
Graphics card provides display output to your monitor. There are many graphics card manufactures out there who
release a new card into the market nearly every three to six months as it is one of the most competitive hardware
market. While choosing a graphics card consider what you would be using it for. For 2D applications such as wordprocessing,
spreadsheet etc, a basic graphics card with around 8MB or 16MB graphics memory will be sufficient for
your needs. It will also allow you to run your monitor at various resolutions. However, if you require 3D functionality for
running 3D applications or playing 3D games you will require a 3D graphics card with at least 128MB or even 256MB
of video memory.
You can buy graphics card with a PCI , AGP or PCI-Express bus. However, most current motherboards have AGP or
PCI-E slot and you should therefore use an AGP or PCI-E graphics card if your motherboard has an AGP or PCI-E
slot. PCI Express graphics card offers much higher graphics bandwidth which results in higher performance. The
current top end graphics card are made by Nvida (Geforce cards) and ATI (Radeon cards). The graphics card that we
will use for our demonstration PC is a GEFORCE II 64MB AGP card as shown below.
Sound card
If you require sound for your PC then you will need a sound card. As basic sound cards are very cheap it is
recommended that you consider a sound card. It offers many benefits such as running multimedia applications with
sound, listening to wave, midi, and MP3 music files or even play your audio CD’s. If you are thinking of playing games
on your PC then having a sound card is a must. Most current motherboards also have basic built in sound. One of the
most popular sound cards are the Creative’s soundblaster range. We will use a Creatives Sounblaster Live 1024 for
our demonstration PC as shown below.
Modem
Modem stands for Modulator Demodulator. It converts digital signals to analogue so that it can travel via your
telephone line, and vice-versa. A modem is an essential item if you are intending to connect your PC to the internet.
There are many kinds modems out there based on the Rockwell/Connexant v.90 chipset. There are two kinds of
modem, software and hardware. Software modems uses your CPU resources to perform its tasks and is run on a
virtual COM port. Hardware modem performs its tasks using the onboard chipset and therefore does not take up the
CPU resources. It also runs on a physical COM i.e. communication port 3. Software modems, which are also known as
winmodem can only run on a windows operating system, while the hardware based modem can run on other operating
systems like linux. External modems are mostly hardware based and connect to the serial port. You can also get
external modems that connect to the USB port, however most of these are software based.
Analogue modems are currently on the decline as they are being replaced by Digital modems which are used for high
speed broadband internet. Also known as ADSL modem or ADSL routers. ADSL modems are mostly external although
you can get Internal ADSL modem’s. Many people are also using Wireless ADSL routers as it offers an excellent way
to share internet connections with multiple PCs. Some common ADSL Router suppliers are Netgear, Belkin and DLink.
I have decided to use a Connexant 56K v.90 software modem for our demonstration PC as it performs quite well in
terms of download.
Ethernet Cards
Ethernet cards are usually purchased separately from a computer, although many computers (such as the Macintosh)
now include an option for a pre-installed Ethernet card. Ethernet cards contain connections for either coaxial or twisted
pair cables (or both) (See fig. 1). If it is designed for coaxial cable, the connection will be BNC. If it is designed for
twisted pair, it will have a RJ-45 connection. Some Ethernet cards also contain an AUI connector. This can be used to
attach coaxial, twisted pair, or fiber optics cable to an Ethernet card. When this method is used there is always an
external transceiver attached to the workstation. (See the Cabling section for more information on connectors.)
FDD
You need a FDD to access floppy disks. Although floppy disks are limited in capacity, only 1.44 mb, every old PC is
almost guaranteed to have a FDD. Floppy disk drives and now coming the end of their life span as some current PCs
are built without a floppy drive. This is due to the popularity of USB Flash drives. Floppy disk is ideal for storing small
files and documents, creating boot disks, and transferring small files. It really does not matter which make of FDD you
purchase as they are cheap and performs the same task.
Hard disk drive
Hard disk drive stores all your data including operating system, applications, user files and documents. It is a nonvolatile
storage, which means the contents of the HDD is not lost if the PC is switched off.
There are three different types of HDD, which are IDE/ATA, SCSI, SATA (Serial ATA). Majority of home PCs are
equipped with IDE Hard drives. SCSI hard drives are mostly included in servers and powerful workstations as they
offer better data transfer rate which results in better performance than the IDE drives. However modern SATA drives
are not far behind SCSI drives in terms of performance with the introduction of the newer SATA 300 drives.
The price of IDE/SATA drives have fallen quite dramatically in the recent years. You can buy a very large drive for a
competitive price. It is better to buy a drive which is quite large as it works out cheaper. A recommended entry level
drive would be 80 GB to 120 GB. The major HDD manufacturers are IBM, Seagate, Maxtor, Western Digital and
Fujitsu. For our demonstration PC I have chosen use an IBM ATA100 drive as shown below.
CD-ROM drive
Nearly all operating systems and applications software comes on CD. It is therefore essential to have a CD-ROM drive
for installing your applications. Certain programs requires the CD to be in the CD-ROM drive for that program to run.
For example, various encyclopedia and games. CD-ROM can also be used for playing standard audio CD’s on your
PC.
If you are intending to watch DVD movies on your PC then you would require a DVD-ROM which can perform all the
tasks of a CD-ROM as well as play DVD movies.
CD-ROM’s come in various speeds, the faster drive, the faster it will install your applications. DVD drives specifies two
types of speeds, one for the software installation and other for the DVD extraction. For example a DVD drive with
16×32x specification means that it is a 16 speed DVD and 32 speed CD. Some of the CD/DVD-ROM manufacturers
include Toshiba, Poineer, Hitachi, LG and Samsung.
PC speakers
A quality sound card would not be much of a benefit without a decent pair of PC speakers. Most PC speakers are
magnetically shielded so that it does not interfere with your monitor, but there are some budget speakers out there that
are not shielded, so check before you buy. If you are just going to use the speakers for basic sound and music and are
not one of those people who play CDs on a PC then you can get away with a budget PC speaker. However, if you play
games and CD’s then you should consider a speaker system with a sub-woofer. These would produce high quality
sound suitable for most tasks.
Monitors
It is important that you get a quality monitor that is comfortable to view. Monitors come is various sizes and refresh
rate. 17″ monitor are becoming entry standard monitor. 15″ monitors are OK if you are running it at a low resolution and
not using it for long hours. As monitor prices have dropped in the recent months it is recommended that you consider a
17″ or 19″ monitor. You can run these monitors at higher resolution and refresh rate, which means they are more
comfortable to view and you can work with them for long hours. Monitors are measured diagonally. If a monitor is 17″ it
does not mean that it is the actual viewable area. Some 17″ comes with a viewable area of 16″ which is good where as
others can be as low as 15.6″. Monitors consist of thousands of pixels (the tiny dots you see on the screen). Smaller
pixels produces high definition sharp display. Settle for something which is at least 0.25 mm dot pitch. If you purchase
a 17″ monitor make sure it can handle refresh rate of at least 85 Hz at 1024 * 768 resolution. A 19″ monitor should
handle at least 1280 * 1024 at 85 Hz.
Currently the most popular viewing device are TFT Flat panels. They are now more affordable than before. Most
people prefer TFT Flat panels as they save lot of desk space. They are also more comfortable view.
CD Writer / DVD Writer
CD Writer / DVD Writer is a very good option for a backup device. It allows you to backup the contents of your HDD
onto a CD-R, CD-RW & DVD-R disc. It also allows you to backup your existing application CD’s. As blank CD’s are
very cheap, it is an affordable backup device.
Like all other PC hardware a CD/DVD Writer comes in various speed. A 32 speed drive can write a full 650MB CD in
around 4 mins and a 52 speed drive can write it in around 3 mins and so on. CD-ReWritable’s are available in IDE and
SCSI interface. You will require a SCSI card if choose to get a SCSI model.
CD / DVD Writer is more than just backup device, you can use it to create your own Audio CD, Photo CD, Video CD
etc. You can also use your CD or DVD meida just the way you use hard drive, using the usual drag and drop file copy.
Most CD/DVD writers are bundled with software which can perform all the tasks I have mentioned.
ZIP drive
If you need to transfer large files from one PC to another, you will find floppy disks quite useless due to their limited
storage capacity. A ZIP drive could be your answer as ZIP disks can store 100 or 250 MB depending on which model
you choose. ZIP disks look similar to floppy disks but are slightly larger. Data can be written and read from a ZIP disk
much quicker than a floppy disk. ZIP disks can be used in the similar manner to floppy disks which makes it a simple
easy to use backup device.
Zip drives have now become obsolete due to writ able CD and DVD. A much more popular option is to use USB Flash
drive also know as Pen Drive.
TV card
A TV card gives you the option of watching TV on your monitor. TV cards are quite useful as it offers more than just
watching TV. You can connect your VCR to the TV card so that you can watch video’s too. One of the useful things
about having a TV card is that you can use it for capturing Video. Using the necessary software you can capture video
in various format such AVI or MPEG files. One of the popular TV card is Haupauge WinTV PCI as shown below.
Older TV cards were all analogue device. Now you can get Digital TV cards which allows you to view Digital terrestrial
TV channels. You can even get Digital Satellite and Cable TV cards.
Assembling the Hardware
If you have purchased all the necessary hardware your are ready assemble your PC. Before unpacking your
components from its original anti-static bags you must put on your anti-static wrist strap, which will discharge your self.
It is important that you discharge yourself or there is a danger that you can damage your components by anti-static
shock by touching the components. If you don’t have an anti-static wrist strap you can discharge your self by touching
the metal edges of your ATX case, although this is not recommended.
Now you can proceed to the first step Motherboard Installation.
The first thing you should do is unpack your ATX case. Take off the cover of your case so that you can access the
inside. Place the case on a desk so that you are looking down towards the open case. Your case should come with
motherboard mounting screws. If your ATX back plate it not already fitted you can fit it by placing your plate near the
ATX back plate cut out and pushing the plate outwards, it should clip on.
Now place your motherboard on top of the mounting screw holes. Make sure your ATX devices on the motherboard
such as PS/2 and parallel port are facing towards ATX back plate cut out. Gently push your motherboard towards the
cut out, every devices should fit easily into its corresponding cut out, as shown below.
The screw holes on your motherboard should align with the screw holes on your case. Place your screws that came
with the case into the appropriate holes and gently screw it on using a screw driver.
The motherboard is now securely mounted to the case. You can now place the ATX power connector to the
motherboard. Your ATX case should come with a power supply unit (PSU) and should already be mounted to the case.
The ATX power connector is shown on image below.
Place the ATX power connector on top of the power socket on the motherboard. Push down the power connector and it
should clip onto the socket. If you try to fit the power connector the wrong way round, it won’t fit, it will only fit one way.
So, if the power connector does not go in, it should go in the other way round.
Next – Processor (CPU) Installation
Locate the processor socket on your motherboard. I am installing an Intel PIII 866 processor on a socket 370 as shown
on the following image. The installation would be slightly different if you have a different processor i.e. Slot1 PIII CPU,
P4 CPU, AMD Slot A / Socket A CPU etc.
Raise the brown lever on the socket and slowly put the processor in place. You have to make sure the pin 1 of your
CPU goes into the pin 1 of your CPU socket otherwise the CPU would not get into the socket, so don’t try to force it in.
It will go in gently if you fit it correctly. Now close the brown lever which will securely hold the CPU in place. If you
bought a retail boxed CPU it would include a heatsink + fan. If you bought an OEM CPU make sure you got a fan that
is correct for the speed of your CPU, otherwise your CPU will overheat and behave abnormally or could be damaged.
Take off the plastic cover from the bottom of the CPU fan that covers the heat transfer pad. Now place the CPU fan on
top the CPU and push down the metal clips on the fan so that it clips onto the CPU socket.
CPU fan has a power connector which needs to be connected to CPU fan power socket on your motherboard as
shown on the image above.
Finally, you have to specify what frequency (speed) your CPU is running at. This can be done using jumper settings, or
on some modern motherboard it can be done in the BIOS, or your motherboard may have automatic detection for your
CPU frequency. Please refer to your motherboard manual for more details. The motherboard I am using (Abit BX133)
has a dip-stick jumper setting and it can be setup in the BIOS. I have left the jumper setting to default as I will use the
BIOS to specify the CPU frequency. The CPU runs at the bus speed of 133Mhz therefore I will use the settings 133 *
6.5(multiplier) under the BIOS, which will the run the CPU at 866Mhz.
Next – Memory Installation (SDRAM)
Installing memory is quite simple. Find the SDRAM or DDRAM banks on your motherboard, they should look similar to
the banks below. Notice the memory banks has a white clip on each side. Make sure you release the clips so it bends
to each side.
Hold each corner of the SDRAM placing it on top of the bank 1. You will notice that the SDRAM has a cut at the bottom
side, it is there to prevent the memoy going in the wrong way round. If you are holding the SDRAM the incorrect way
you will not be able insert it. Gently push down the SDRAM and it should clip on to the memory bank. The two white
clips will now become straight holding each corner of the memory. If you have more that one SDRAM perform same
steps as above but placing the SDRAM in memory bank 2 and so on.
Next – Hard Disk Drive Installation
If you look at the rear side of an IDE hard drive it should look similar to the image below.
The IDE/ATA connector is on the left hand side which consists of many pins. Next to the IDE connector is the jumper
setting for the drive. The jumper should be set to Master, which is the default setting for a new HDD. Any other device
sharing the same IDE cable should be set to Slave. Different HDD has different jumper settings, please refer to your
HDD manual for more information. On the right hand side, next to the jumpers is the power connector. Every device
except FDD uses this type of power connector. Figure 1 and 2 below shows what an ATA 66 and a power cable looks
like. The ATA 66 cable which is also known as UDMA 66 cable is an advance IDE cable, which offers higher
performance and data integrity than the standard IDE cable. ATA 66 cable consists of 80 conductor cable where as the
standard IDE cable consists of 40 conductor cable. I am using an ATA 66 cable because the above HDD is an ATA
100 drive which requires an ATA 66 cable.
Figure 1 – ATA 66 Cable
Figure 2 – Power cable
Place your hard drive into the HDD mounting slot of your case, make sure the IDE/ATA connector is facing outwards.
Screw the HDD to the case using screws provided with the HDD or the ATX case.
Insert the ATA 66 cable into the ATA connector of the HDD. Make sure the pin 1 on the cable is connected to pin 1 on
the HDD connector. Pin 1 is the red or pink strip on the edge of an ATA cable. Most new IDE/ATA cables are designed
so that it will only go in one way which will correspond to pin 1.
Push the power cable into the power connector as shown. The power cable is designed to go in one way, so you
shouldn’t have any problems.
Connect the other end of the ATA 66 cable to the primary ATA socket of your motherboard as shown. Make sure the
pin 1 on the cable connects to the pin 1 on the ATA socket.
That’s it you have successfully installed a HDD.
Next – Floppy Disk Drive Installation
The rear side of a floppy drive looks similar to the following image.
The black connector on the left hand side is the floppy disk connector. It is different from the IDE connector and uses a
different cable. The small white connector on the right hand side is the power connector for the floppy drive. Figure 1
and 2 below shows what a floppy drive cable and floppy drive power connector looks like.
Figure 1 – Floppy drive cable.
Figure 2 – Floppy drive power cable
Place the floppy drive into the FDD mounting slot as shown. Screw the drive securely into place.
Insert the floppy drive cable into the floppy drive connector. Make sure the pin 1 on the cable connects to the pin 1 on
the floppy drive connector. As you already know by now that pin 1 is the red or pink strip on the edge of the floppy drive
cable. Most floppy drive cables are designed so that it will only go in on way, so you can not connect it incorrectly.
Push the floppy drive power cable to the power connector. This will only go in on way.
Finally connect the other end of the floppy drive cable to floppy drive connector on your motherboard. Make sure pin 1
on the cable connects to pin 1 on the connector.
Next – CD-ROM/DVD-ROM Installation
If you look at the rear side of your CD / DVD-ROM it should look similar to image shown on figure 1.
Figure 1
On the right hand side you have the power connector. Next to power connector you have the IDE connector. On the
left hand side near the IDE connector you have the jumper settings for the DVD-ROM. The jumper is set to Master by
default. I am connecting the DVD-ROM on a separate IDE cable therefore I will leave the jumper setting to Master.
However if you are sharing an IDE cable with another device like HDD, then you would have to set jumper to Slave, as
your HDD would be set to Master. Next to the jumpers you have the CD Audio-Out socket. One side of your audio
cable connects to this socket and other side connects to the sound card cd-in socket. This would allow you to listen to
Audio CD’s on your computer.
Figure 2
Mount your CD/DVD-ROM drive into its mounting slot. Use the supplied screws to screw the drive into position.
Figure 3
Connect the IDE cable to the drives IDE connector. Make sure the pin 1 on the cable is connected to pin 1 on the
drives IDE connector. Pin 1 is the red or pink strip on the edge of an IDE cable. Connect the other end of the IDE cable
to the IDE socket on your motherboard as shown in figure 4. Again, make sure you conncet the cable to pin 1. The IDE
socket could be your primary or secondary socket depending which socket you choose. If your HDD is on the primary
IDE socket and your secondary IDE socket is free, then it is better to use your secondary IDE socket for the CD/DVDROM.
Figure 4
Finally connect the power cable to power connector and connect the audio cable to the CD Audio-Out socket as shown
on figure 3.
Next – Graphics card installation
Most modern graphics cards are AGP based and connects to the AGP bus of the motherboard. An AGP bus (slot)
looks like the following image. The brown slot is where you connect your AGP graphics card.
Place your AGP card on top of the slot and gently push it down. The card should firmly sit into position.
All you need to do now is to screw the metal plate on the front of the card to the ATX case. Use the screws supplied
with case and screw the card to the case.
Next – Sound card Installation
Most modern sound cards are designed with the PCI interface and connects to the PCI slot of your motherboard. A PCI
slot looks like the slots on the following image.
Place your sound card on top of a chosen slot. Gently push down the card so it sits into position. Once the card is
seated correctly into position, screw the card on to the case.
Finally insert the audio cable into the CD-IN socket. The other end of the cable should be connected to Audio-out
socket on your CD/DVD-ROM drive.
Next – Modem Installation
Find a free PCI slot on your motherboard (assuming your modem is a PCI modem). Place your modem card on top of
the slot and gently push it down into position.
Once the card has seated correctly into position, screw the card to the case using the screws supplied with the case.
Now you have installed all the prerequisite hardware devices. You can either proceed to the finalising stage, or you
may want to install optional devices like a ZIP drive, CD-RW drive or a TV-Card. If you do not want to install these
devices you can now proceed to the finalising stage.
Next Finalising stage
Now that you have installed all the necessary hardware there are still few more things you need to do before switching
on your PC for the first time. Your ATX case has a power switch which turns the PC on, a reset switch for resetting the
system, a power LED which comes on when the PC is switched on and a hard drive LED which flashes when data is
being written or read from your hard drive. You also have an internal speaker.
Figure 1 – Power and Reset switch
The switches and LED’s need to be connected to its corresponding connectors on the motherboard. Please refer to
your motherboard manual to locate where the connectors are. Different motherboards place the connectors in different
locations. The connectors for the switches and LED’s are normally grouped together. They should look similar to the
image below.
Figure 2 – Switch and LED connectors
Every cable is normally labeled, they are normally named as follows, but could be slightly different on your system.
Power switch Power / PWR-SW
Reset switch Reset
Power LED Power LED / PWR-LED
Hard drive LED HDD-LED / IDE LED
Speaker SPK / Speaker
The connectors on the motherboard are also labeled but may be too small to see. Instead refer to your motherboard
manual which would provide details on which pins you should connect the cables to. The image below shows how the
pins may be organised on your motherboard.
Once you have connected all the cables to the correct pins on the motherboard, you are ready to switch the PC on. At
this point you can close the cover of your ATX case but don’t screw it on just yet as you might have possible problems
that needs rectifying. Connect all the cables to back of ATX case. These includes the main power cable that connects
to the power supply. PS/2 mouse and keyboard that connects to the PS/2 ports. Monitor cable that connects to the
graphics card port, etc. Finally the moment has arrived. Switch on your monitor first. Your ATX power supply might
have a main power switch at the back so make sure that is switched on. Now switch the PC on by pressing the power
switch on the front of the ATX case. If you have performed all the tasks without any mistakes and providing that none
of the main components are faulty, the PC should boot. When the PC boots you should see the name of the BIOS
manufacturer, such as AWARD BIOS displayed on your monitor. Your CPU type, speed and the amount of memory
should be displayed as shown on image below.
If your motherboard has a plug and play BIOS and is set to automatic device detection by default, then you would see
your IDE devices being detected followed by a prompt complaining about missing operating system. If your
motherboard does not detect the hardware, then you need to proceed to the BIOS setup screen by pressing DEL or F1
or F2 depending on your motherboard. Congratulations you have completed building your own PC. You now need to
proceed to the software section which explains how to setup the BIOS, Hard disk and install an operating system.
If things did not go smoothly and your PC does not switch on then go to the troubleshooting section for possible
solutions.
Software
After assembling your PC you need to setup the BIOS, hard disk, and load an operating system to get your PC up and
running. The tasks required are as follows:
1. BIOS Setup
2. Hard disk partition and format.
3. Installing Windows 98 / ME
4. Installing Windows XP
Award BIOS Version 6.00PG Setup
This is the BIOS setup for Award BIOS v6.00PG. If you have a different version of the Award BIOS their would be a lot
of similarities. If your BIOS is AMI or Phoenix then the common BIOS features would have some similarities. Whatever
BIOS you have, this setup guide should give you an idea about how to setup a BIOS. Please note that setting up BIOS
incorrectly could cause system malfunction, therefore it is recommended that you also follow the BIOS guide provided
on your motherboard manual.
Click on any of the BIOS setup options below to setup that feature.
Softmenu III Setup PC Health Status
Standard CMOS Features Load Fail-Safe Defaults
Advanced BIOS Features Load Optimized Defaults
Advanced Chipset Features Set Password
Integrated Peripherals Save & Exit Setup
Power Management Setup Exit Without Saving
PnP/PCI Configurations
Softmenu III
Softmenu III is where you can setup up the CPU without setting jumpers on the motherboard. You can setup the CPU
simply by selecting the speed i.e. Pentium III 750 from the list. This ensures that the CPU bus, multiplier, voltage etc, is
correctly set for that particular CPU. However you can manually setup each feature if required. Once you have finished
with the setup press ESC to return the previous menu. See figure 1.
Figure 1: SoftMenu III Setup
Standard CMOS Features
Here you can setup the basic BIOS features such as date, time, type of floppy etc. Use the arrow keys to move around
and press enter to select the required option. You can specify what IDE devices you have such as Hard drive, CDROM,
ZIP drive etc. The easiest way to setup the IDE devices is by leaving it set to auto. This allows the BIOS to
detect the devices automatically so you don’t have to do it manually. At the bottom, it also displays the total memory in
your system. See figure 2.
Figure 2: Standard CMOS Features
As you can see from figure 3, there are numerous advance settings which you can select if required. For most cases
leaving the default setting should be adequate. As you can see the first boot device is set to floppy. This ensures that
the floppy disk is read first when the system boots, and therefore can boot from windows boot disk. The second boot
device is the Hard disk and third is set to LS120. If you want to boot from a bootable CD then you can set the third boot
device to CD/DVD-ROM. See Figure 3.
Advanced Chipset Features
Here you can setup the contents of the chipset buffers. It is closely related to the hardware and is therefore
recommended that you leave the default setting unless you know what you are doing. Having an incorrect setting can
make your system unstable. If you know that your SDRAM can handle CAS 2, then making changes can speed up the
memory timing. If you have 128MB SDRAM then the maximum amount of memory the AGP card can use is 128MB.
See Figure 4
Figure 3: Advanced BIOS Features
Figure 4: Advanced Chipset Features
Inegrated Peripherals
This menu allows you to change the various I/O devices such as IDE controllers, serial ports, parallel port, keyboard
etc. You can make changes as necessary. See figure 5.
Figure 5: Integrated Peripherals
Power Management Setup
The power management allows you to setup various power saving features, when the PC is in standby or suspend
mode. See figure 6.
Figure 6: Power Management Setup
PnP/PCI Configurations
This menu allows you to configure your PCI slots. You can assign IRQ’s for various PCI slots. It is recommended that
you leave the default settings as it can get a bit complicated messing around with IRQ’s. See figure 7.
Figure 7: PNP/PCI Configurations
PC Health Status
This menu displays the current CPU temperature, the fan speeds, voltages etc. You can set the warning temperature
which will trigger an alarm if the CPU exceeds the specified temperature. See figure 8.
Figure 8: PC Health Status
Load Fail-Safe Defaults
If you made changes to the BIOS and your system becomes unstable as a result, you can change it back to default.
However if you made many changes and don’t know which one is causing the problem, your best bet is to choose the
option “Load Fail Safe Mode Defaults” from the BIOS menu. This uses a minimal performance setting, but the system
would run in a stable way. From the dialog box Choose “Y” followed by enter to load Fail-Safe Defaults.
Load Optimized Defaults
Like the Fail-Safe mode above, this option loads the BIOS default settings, but runs the system at optimal
performance. From the dialog box Choose “Y” followed by enter to load Optimized Defaults.
Set Password
To password protect your BIOS you can specify a password. Make sure you don’t forget the password or you can not
access the BIOS. The only way you can access the BIOS is by resetting it using the reset jumper on the motherboard.
Save and Exit Setup
To save any changes you made to the BIOS you must choose this option. From the dialog box choose “Y”.
Exit without Saving
If you don’t want to save changes made to the BIOS, choose “N” from the dialog box.
Hard Disk Setup – Partition and Format
This procedure explains how to setup a new hard disk. Warning – if you are setting up a hard disk which contains data,
the following procedure would completely erase your hard disk and the data would be unrecoverable.
Before a new hard disk can be used it needs to be setup. This involves partitioning and formatting the hard disk.
Windows 98 or ME boot disk contains the required software to perform this procedure. FDISK.EXE and FORMAT.COM
are the files required in your bootable floppy disk. Start the partition and format procedure by booting your PC using a
Windows boot disk. Make sure you set the BIOS so that the boot sequence is set to detect the floppy disk first. If your
system has no problems booting you will be presented with a Windows boot disk menu. This gives you the option to
start the system with or without CD-ROM support. At this stage you do not need the CD-ROM support, so choose the
option to boot without CD-ROM support. You should end up in the MS DOS prompt A: (A drive). From A: command
prompt type fdisk. You will be presented with following message:
Choose “Y” to enable large disk support.You will now be presented with the FDISK main menu as shown below.
From the menu, choose option 1 – Create DOS partition or Logical DOS drive. Another menu will present the following
options.
Choose option 1 – Create primary DOS Partition. FDISK verifies the integrity of your drive and will ask you if want to
use the maximum available size of your hard disk to create the primary partition and set it active. To keep things simple
we will create one large partition. Choose “Y” to use maximum available space. When the partition has been created
successfully you will be notified by the system. Your drive is now known as C: (C drive). Press “Esc” to return to the
menu. Press “Esc” again to exit FDISK. You need to restart your system for the changes to take affect. Leave boot disk
in the drive.When the system reboots, choose start without CD-ROM from the boot disk menu. While booting from
floppy disk you might get error message like “Invalid media type reading drive C” this is OK for this stage as the hard
disk is not formatted.
From A: command prompt type format c:You will get a message saying “WARNING, ALL DATA ON NONREMOVABLE
DISK DRIVE C: WILL BE LOST. Proceed with Format (Y/N)?”.
Don’t worry about the message as you do not have any data in the new hard disk. Choose “Y”. The format will proceed
and would show you a progress indicator. The time it takes to format a hard disk depends on the size and speed of the
drive. This could be around 5-30 minutes. Once the format is complete you need to reset your system. You are now
ready to install an operating system.
Installing Windows 98/ME Operating System
This procedure demonstrates how to install Windows ME operating system. The procedure to install Windows 98 is
very similar to ME. Since Windows ME is the latest Windows 9x family operating system, it will be used to demonstrate
the installation procedure.
Boot your system with Windows 98 or ME boot disk. When the system starts you will be presented with a menu which
gives you the option to boot with or without CD-ROM support. Select the option to boot with CD-ROM support. This
would create a RAM drive and load a device driver to support your DVD/CD-ROM. The RAM drive is assigned to D: (D
drive) and your CD-ROM should be assigned to E: (E drive).
Place the Windows ME CD into the drive. At A: command prompt type E: and press enter. Then type setup. At his
stage Windows runs DOS based scandisk to verify if your hard disk has any problems. If there are no problems
Windows proceeds with the setup and launches the Windows ME setup wizard as shown in figure 1.
figure 1: Windows ME Setup Wizard
After agreeing to the license agreement Windows will ask you to type in your product key. The default directory to
install windows is c:\windows, I recommend that you leave it as default. Next you would be given four types of
installation options which are Typical, Portable, Compact, and Custom. Choosing typical would install the most
common components and is suitable for most people. If you want to specify which components to install then choose
custom. You would be presented with few other dialog boxes such entering your name and company name, option to
create a Windows ME boot disk before file copy process begins. After completing the copying process Windows
restarts and boots from the hard disk, make sure you remove your floppy disk from the drive. It will detect your plug
and play devices and would present a few more dialog boxes. Just read the instructions on dialog boxes and proceed
as required. Windows would restarts again after completing final setup stage. This does not mean everything is
completely setup. Some of your hardware device may have conflicts or may not have drivers loaded as Windows does
not contain those drivers.
From device manager you can check if all the drivers has been loaded or if there are any conflicts. From the start menu
select Start -> Settings -> Control Panel. Click on the System icon and then from the System Properties window
select the Device Manager tab. This lists all the devices as shown in figure 2.
Figure 2: Windows Device Manager
If there are any yellow exclamation mark “!” next to any of the listed device, it means that no drivers or incorrect drivers
has been loaded for that device. Your hardware should come with manufacturer supplied drivers. You need to install
these drivers using automatic setup program provided by the manufacturer or you need to manually install these
drivers. If you do not have the drivers, check the manufacturers website to download them.
To install a driver manually use the following procedure:
1. From the device manager double click on the device containing the exclamation mark.
2. This would open a device properties window.
3. Click on the Driver tab.
4. Click Update Driver push button. The Wizard for updating device driver pops up as shown in figure 3.
5. You now get two options. The first option provides an automatic search for the required driver. The second
option allows you to specify the location of the driver. If you don’t know the location of the driver choose the
automatic search which would find the required driver from the manufacturer supplied CD or Floppy disk.
Windows would install the required driver and ask you to restart the system for the changes to take affect.
Use this procedure to install drivers for all the devices that contain an exclamation mark. Windows is
completely setup when there are no more exclamation marks in the device manager.
Figure 3: Installing Device Driver
Installing Windows XP Professional
This procedure demonstrates how to install Windows XP Professional. The procedure to install Windows XP home
edition is very similar to the professional edition. Since Windows XP Pro is more advance operating system, it will be
used to demonstrate the installation procedure.
The best way install Windows XP is to do a clean install. It is not difficult to perform a clean installation. Before you
perform the installation I recommend that you check Windows XP Compatibility List to ensure that your hardware is
supported by XP. If your hardware is not on the compatibility list you can check your hardware manufactures website to
download the drivers for Windows XP. Save all the necessary drivers onto floppy disks or CD before you start the
installation.
All versions of Windows XP CD are bootable. In order to boot from CD-ROM you need to set the boot sequence. Look
for the boot sequence under your BIOS setup and make sure that the first boot device is set to CD-ROM. If you have
an older PC and your BIOS does not support boot from CD-ROM then you need to create boot disks using 6 floppy
disks. You can download the following program from Microsoft which will create the 6 floppy setup disks:
Windows XP Home Edition – www.microsoft.com/downloads/release.asp?releaseid=33290 />Windows XP Professional – www.microsoft.com/downloads/release.asp?releaseid=33291 />If your computer can boot from CD-ROM then you can perform the following steps to install Windows XP:
1. Start your PC and place your Windows XP CD in your CD/DVD-ROM drive.
2. Your PC should automatically detect the CD and you will get a message saying “Press any key to boot from CD”.
3. Press a key to boot from CD and Windows setup will begin. Windows will start copying preliminary setup files to your
computer.
4. You will be asked if you want to perform a new installation, repair an existing installation, or quit. In this case, you
will be performing a new installation.
5. You will be presented with the End User Licensing Agreement. Press F8 to accept and continue.
6. Select the partition where you want install windows. You will have the opportunity to create and/or delete partitions
or just allocate the available disk space to one partition.
7. The next screen asks if you wish to use the NTFS file system. This is the recommended file system. If you choose to
use FAT32, you will not have all the security and stability features of Windows XP.
8. Choose to format the partition to either FAT32 or NTFS. You’ll also see two additional choices to perform a quick
format of each option. Stick with doing a full format. When asked to start the format, press the “F” key. The formatting
process may take quite a bit of time depending on the size of your HDD.
9. The setup program will automatically start copying files after the partition is formatted and you will see a setup
progress bar.
10. After this is complete the computer will restart. Leave the XP CD in the drive but this time DO NOT press any key
when the message “Press any key to boot from CD” is displayed. In few seconds setup will continue.
11. Windows XP Setup wizard will guide you through the setup process of gathering information about your computer.
12. Choose the region and language.
13. Type in your name and organization.
14. Enter your product license key.
15. Name the computer, and enter an Administrator password. Don’t forget to write down your Administrator password.
16. Enter the correct date and time.
17. Choose workgroup or domain name.
18. Register Windows XP if you’ve installed all the current hardware on your machine.
19. Add users that will sign on to this computer.
20. Log in, to your PC for the first time. You now need to check the device manager to confirm that all the drivers has
been loaded or if there are any conflicts. From the start menu select Start -> Settings -> Control Panel. Click on the
System icon and then from the System Properties window select the Hardware tab, then click on Device Manager.
This lists all the devices as shown in figure 1.
figure 1: Windows XP Device Manager
If there are any yellow exclamation mark “!” next to any of the listed device, it means that no drivers or incorrect drivers
has been loaded for that device. Your hardware should come with manufacturer supplied drivers. You need to install
these drivers using automatic setup program provided by the manufacturer or you need to manually install these
drivers. If you do not have the drivers, check the manufacturers website to download them.
To install a driver manually use the following procedure:
(a) From the device manager double click on the device containing the exclamation mark.
(b) This would open a device properties window.
(c) Click on the Driver tab.
(d) Click Update Driver push button. The Wizard for updating device driver pops up as shown in figure 2.
figure 2: Installing Device Driver
You now get two options. The first option provides an automatic search for the required driver. The second option
allows you to specify the location of the driver. If you don’t know the location of the driver choose the automatic search
which would find the required driver from the manufacturer supplied CD or Floppy disk. Windows would install the
required driver and may ask you to restart the system for the changes to take affect. Use this procedure to install
drivers for all the devices that contain an exclamation mark. Windows is completely setup when there are no more
exclamation marks in the device manager
Troubleshooting
Below is a list of common problems experienced while assembling a PC. Please check the list which could have the
possible solution to your problems.
Problem: The PC does not boot, the power and HDD LED does not come on, there is no display on monitor.
Solution: Check that your main power cable is plugged into the ATX power supply. Make sure you have connected the
ATX power connector to the motherboard. Check if the cable for the power switch at front of the PC is connected to the
correct pins on the motherboard.
Problem: The power LED comes on but the PC does not boot, there is no display on monitor.
Solution: Check if the processor is firmly into the socket. Check CPU jumpers to verify if CPU frequency is correctly
set.
Problem: The PC does not boot, but is beeping.
Solution: Different BIOS manufacturers use various number of beeps to indicate faults with various hardware. In an
Award BIOS motherboard you will get following beeps:
1 long 2 short: Graphics card is not securely into place, or faulty.
1 long 3 short: Graphics card is not securely into place, or faulty video memory.
Continuous beeps: No memory, or memory not securely into place, or could be faulty.
Continuous high/low beeps: No CPU, or CPU not securely into place, or could be faulty.
Please refer to your motherboard manual to confirm what the beeps are trying to tell you.
Problem: The PC boots but the CPU speed is incorrect.
Solution: The CPU frequency jumper setting is incorrect. Refer to your motherboard manual to set it correctly.
Problem: The HDD is not being detected by the BIOS.
Solution: Check if you connected the IDE cable to the motherboard correctly, is pin 1 on the IDE cable connected to
pin 1 on the IDE sockets on both motherboard connector and HDD connector. Check if the HDD jumper is set to
master and any other device sharing the same cable is set to slave. Please refer to Hard disk installation section for
more details
Problem: I can not access my CD/DVD-ROM in DOS mode, hence can not install Windows.
Solution: CD/DVD-ROM device driver is not installed. Install the manufacturer supplied device driver. If you do not
have a device driver disk, you can use the windows boot disk which will provide access to your CD/DVD-ROM, so that
you can install Windows.
Chapter Three
Computer System Troubleshooting and Maintenance
There are two types of people who need to learn computer problem troubleshooting.
1. PC users who want to troubleshoot their computer problems.
You may be having a computer problem which you need to do a quick computer troubleshooting and fix it. This is a
vast area.
2. Those who want to learn computer troubleshooting in-depth.
Probably you want to start from very basic and learn up to advance techniques and do computer troubleshooting like a
pro. Then below information is for you.
Computer Hardware Troubleshooting
This computer hardware troubleshooting section will help you if you have a computer problem and need a quick fix.
It is hard to separate computer hardware with the Operating System. So this section will also have tips for computer
software troubleshooting.
The computer hardware troubleshooting steps listed below are only for PCs with Windows Operating System.
Basic Computer Hardware Troubleshooting Guidelines
Ideally, once you have installed your hardware, you can simply use it—over and over again—without any need to dig
into the Windows settings and make changes. Unfortunately, all too often, this ideal falls somewhat short of what
actually happens. Sometimes, you have to reconfigure your hardware. Other times, you must reinstall it in order to get
it to work. At still other times, you don’t have a problem at all; you simply want to upgrade the software components to
take advantage of new or improved features. Windows XP offers a number of wizards and dialog boxes to help you
work with your hardware’s drivers and settings. The most important tool, Device Manager, provides a central focus for
this chapter.
Windows XP also contains a number of tools for maintaining your system. Because your hard drives constitute the
single most important hardware component to maintain, this chapter also covers hard disk maintenance tools. Between
the Device Manager and the hard drive utilities, you can keep the hardware on your system working smoothly.
What is Device Manager and how to use it for computer hardware troubleshooting?
Without a doubt, the Windows Device Manager serves as your best friend in uncovering and solving hardware
problems. Device Manager displays a list of all your hardware arranged in categories with each item accessible by
locating the correct category and expanding it by clicking the plus sign (+) to its left. Device Manager’s usefulness
comes to the fore when a device malfunctions. To open Device Manager (in Windows XP), click start button, rightclick
My Computer, and choose Properties. From the resulting System Properties dialog, click the Hardware tab.
In the Device Manager section of the dialog box, click the Device Manager button. After a brief delay, the Device
Manager utility will open.
Your first survey of hardware status takes place immediately, according to the following views:
If all categories display closed, with no individual devices showing, Device Manager does not know of any
malfunctioning hardware. The device still might not work, but, from the standpoint of Windows XP, it works just fine.
If Windows XP sees any device as malfunctioning, Device Manager opens with that device’s category automatically
expanded to reveal the problem hardware. After upgrading to Windows XP or installing it for the first time, you should
expect one or more devices to display as nonfunctioning, awaiting drivers.
REPAIRING HARDWARE DEVICES
Device Manager gives you two major options for configuring your hardware devices: configuring the resources it uses
and changing the drivers associated with it. Of these two, updating the driver happens more frequently because
Windows XP has proven itself notably adept at managing system resources. Still, you can adjust system resources
manually if you come across conflicts with the result that you can solve virtually all hardware problems from within
Device Manager, except those in which the hardware itself does not work because of mechanical malfunction.
Tip: If a hardware device stops working completely and you can’t solve the problem in just a few minutes, you might
have a mechanical problem instead of an electronic one. Consider removing the hardware device, and installing it in
another PC if one is available. If the hardware still doesn’t work and you still get no response from it, you can assume
that it has bitten the dust and can be discarded or, in the case of expensive hardware devices such as printers or
monitors, sent to a repair shop.
Computer hardware troubleshooting: Step by Step Troubleshooting RAM (Memory)
It’s rare but RAM modules can cause problems. Unfortunately, it’s not always certain that the memory errors being
reported by your system is actually due to problems with the RAM modules. Even worse is that an unstable system can
be due to many problems including RAM failure.
Step 1: Back up all important files and data. You should be doing this on a regular basis anyway but if your computer is
showing signs of failure don’t wait any longer to perform this job.
Step 2: Start simple and analyze the problem.
• Have you added or replaced RAM?
• Is it installed properly?
• Have you moved the computer? RAM modules can come loose.
• Is it a new computer? RAM modules might not have been inserted properly.
• Have you installed any new hardware upgrades?
• Have you installed new software or might there be a virus problem?
• Have you changed or installed patches for your operating system?
• Do you have the correct RAM type?
• Is the RAM module connectors tin or gold?
• When your computer starts (boots) does it report the correct amount of RAM?
• Does your system properties report the correct amount of RAM?
• Are there any POST messages that indicate RAM problems?
• Does the system report Parity errors or address failures whilst the system is running?
• Do you get a Windows error message “exception error OE at>>0137:BFF9z5d0″ or something similar?
• You’ve tried everything else!!!
Any one of these can indicate a problem with the RAM module or something connected with it.
WARNING: Before you start troubleshooting remember that you are dealing with electricity that can KILL. Only work
inside the computer case when the power has been switched off and disconnected. Never open the power source.
Step 3: S

FRIDAY

computer virus

brief intro on computer virus

A computer virus is a computer program that can copy itself and infect a computer without the permission or knowledge of the owner. The term “virus” is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer. The term “computer virus” is sometimes used as a catch-all phrase to include all types of malware. Malware includes computer viruses, worms, trojan horses, most rootkits, spyware, dishonest adware, crimeware, and other malicious and unwanted software), including true viruses. Viruses are sometimes confused with computer worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda. Worms and Trojans, like viruses, may cause harm to either a computer system’s hosted data, functional performance, or networking throughput, when they are executed. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious. Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today’s viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging, and file sharing systems to spread.

history

Creeper virus was first detected on ARPANET, the forerunner of the Internet in the early 1970s. 

Creeper was an experimental self-replicating program written by Bob Thomas at BBN in 1971. Creeper used the ARPANET to infect DEC PDP-10 computers running the TENEX operating system. Creeper gained access via the ARPANET and copied itself to the remote system where the message, “I’m the creeper, catch me if you can!” was displayed. The Reaper program was created to delete Creeper.

A program called “Rother J” was the first computer virus to appear “in the wild” — that is, outside the single computer or lab where it was created. Written in 1981 by Richard Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread via floppy disk. This virus was created as a practical joke when Richard Skrenta was still in high school. It was injected in a game on a floppy disk. On its 50th use the Elk Cloner virus would be activated, infecting the computer and displaying a short poem beginning “Elk Cloner: The program with a personality.”

The first PC virus in the wild was a boot sector virus dubbed (c)Brain 

, created in 1986 by the Farooq Alvi Brothers, operating out of Lahore, Pakistan. The brothers reportedly created the virus to deter pirated copies of software they had written. However, analysts have claimed that the Ashar virus, a variant of Brain, possibly predated it based on code within the virus

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. PCs of the era would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the wild for many years.

Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS, modem use, and software sharing. Bulletin board-driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBS’s. Within the “pirate scene” of hobbyists trading illicit copies of retail software, traders in a hurry to obtain the latest applications were easy targets for viruses.

Macro viruses have become common since the mid-1990s. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel and spread throughout Microsoft Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS, most could also spread to Macintosh computers. Although most of these viruses did not have the ability to send infected e-mail, those viruses which did took advantage of the Microsoft Outlook COM interface. Some old versions of Microsoft Word allow macros to replicate themselves with additional blank lines. If two macro viruses simultaneously infect a document, the combination of the two, if also self-replicating, can appear as a “mating” of the two and would likely be detected as a virus unique from the “parents.”

A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating.

Cross-site scripting viruses emerged recently, and were academically demonstrated in 2005. Since 2005 there have been multiple instances of the cross-site scripting viruses in the wild, exploiting websites such as My Space, facebook and Yahoo.

Infection strategies

In order to replicate itself, a virus must be permitted to execute code and write to memory. For this reason, many viruses attach themselves to executable files that may be part of legitimate programs. If a user attempts to launch an infected program, the virus’ code may be executed simultaneously. Viruses can be divided into two types based on their behavior when they are executed. Nonresident viruses immediately search for other hosts that can be infected, infect those targets, and finally transfer control to the application program they infected. Resident viruses do not search for hosts when they are started. Instead, a resident virus loads itself into memory on execution and transfers control to the host program. The virus stays active in the background and infects new hosts when those files are accessed by other programs or the operating system itself.

Nonresident viruses

Nonresident viruses can be thought of as consisting of a finder module and a replication module. The finder module is responsible for finding new files to infect. For each new executable file the finder module encounters, it calls the replication module to infect that file.[11]

Resident viruses

Resident viruses contain a replication module that is similar to the one that is employed by nonresident viruses. This module, however, is not called by a finder module. The virus loads the replication module into memory when it is executed instead and ensures that this module is executed each time the operating system is called to perform a certain operation. the replication module can be called, for example, each time the operating system executes a file. In this case the virus infects every suitable program that is executed on the computer.

Resident viruses are sometimes subdivided into a category of fast infectors and a category of slow infectors. Fast infectors are designed to infect as many files as possible. A fast infector, for instance, can infect every potential host file that is accessed. This poses a special problem when using anti-virus software, since a virus scanner will access every potential host file on a computer when it performs a system-wide scan. If the virus scanner fails to notice that such a virus is present in memory the virus can “piggy-back” on the virus scanner and in this way infect all files that are scanned. Fast infectors rely on their fast infection rate to spread. The disadvantage of this method is that infecting many files may make detection more likely, because the virus may slow down a computer or perform many suspicious actions that can be noticed by anti-virus software. Slow infectors, on the other hand, are designed to infect hosts infrequently. Some slow infectors, for instance, only infect files when they are copied. Slow infectors are designed to avoid detection by limiting their actions: they are less likely to slow down a computer noticeably and will, at most, infrequently trigger anti-virus software that detects suspicious behavior by programs. The slow infector approach, however, does not seem very successful.

Vectors and hosts

Viruses have targeted various types of transmission media or hosts. This list is not exhaustive:

Binary executable files (such as COM files and EXE files in MS-DOS, Portable Executable files in Microsoft Windows, and ELF files in Linux) Volume Boot Records of floppy disks and hard disk partitions The master boot record (MBR) of a hard disk General-purpose script files (such as batch files in MS-DOS and Microsoft Windows, VBScript files, and shell script files on Unix-like platforms). Application-specific script files (such as Telix-scripts) System specific autorun script files (such as Autorun.inf file needed to Windows to automatically run software stored on USB Memory Storage Devices). Documents that can contain macros (such as Microsoft Word documents, Microsoft Excel spreadsheets, AmiPro documents, and Microsoft Access database files) Cross-site scripting vulnerabilities in web applications Arbitrary computer files. An exploitable buffer overflow, format string, race condition or other exploitable bug in a program which reads the file could be used to trigger the execution of code hidden within it. Most bugs of this type can be made more difficult to exploit in computer architectures with protection features such as an execute disable bit and/or address space layout randomization.

PDFs, like HTML, may link to malicious code.[citation needed]PDFs can also be infected with malicious code.

In operating systems that use file extensions to determine program associations (such as Microsoft Windows), the extensions may be hidden from the user by default. This makes it possible to create a file that is of a different type than it appears to the user. For example, an executable may be created named “picture.png.exe”, in which the user sees only “picture.png” and therefore assumes that this file is an image and most likely is safe.

An additional method is to generate the virus code from parts of existing operating system files by using the CRC16/CRC32 data. The initial code can be quite small (tens of bytes) and unpack a fairly large virus. This is analogous to a biological “prion” in the way it works but is vulnerable to signature based detection.

This attack has not yet been seen “in the wild”.

Methods to avoid detection

In order to avoid detection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the “last modified” date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.

Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.

Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.

As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access.

Avoiding bait files and other undesirable hosts

A virus needs to infect hosts in order to spread further. In some cases, it might be a bad idea to infect a host program. For example, many anti-virus programs perform an integrity check of their own code. Infecting such programs will therefore increase the likelihood that the virus is detected. For this reason, some viruses are programmed not to infect programs that are known to be part of anti-virus software. Another type of host that viruses sometimes avoid is bait files. Bait files (or goat files) are files that are specially created by anti-virus software, or by anti-virus professionals themselves, to be infected by a virus. These files can be created for various reasons, all of which are related to the detection of the virus:

Anti-virus professionals can use bait files to take a sample of a virus (i.e. a copy of a program file that is infected by the virus). It is more practical to store and exchange a small, infected bait file, than to exchange a large application program that has been infected by the virus. Anti-virus professionals can use bait files to study the behavior of a virus and evaluate detection methods. This is especially useful when the virus is polymorphic. In this case, the virus can be made to infect a large number of bait files. The infected files can be used to test whether a virus scanner detects all versions of the virus. Some anti-virus software employs bait files that are accessed regularly. When these files are modified, the anti-virus software warns the user that a virus is probably active on the system.

Since bait files are used to detect the virus, or to make detection possible, a virus can benefit from not infecting them. Viruses typically do this by avoiding suspicious programs, such as small program files or programs that contain certain patterns of ‘garbage instructions’.

A related strategy to make baiting difficult is sparse infection. Sometimes, sparse infectors do not infect a host file that would be a suitable candidate for infection in other circumstances. For example, a virus can decide on a random basis whether to infect a file or not, or a virus can only infect host files on particular days of the week.

Stealth

Some viruses try to trick anti-virus software by intercepting its requests to the operating system. A virus can hide itself by intercepting the anti-virus software’s request to read the file and passing the request to the virus, instead of the OS. The virus can then return an uninfected version of the file to the anti-virus software, so that it seems that the file is “clean”. Modern anti-virus software employs various techniques to counter stealth mechanisms of viruses. The only completely reliable method to avoid stealth is to boot from a medium that is known to be clean.

Self-modification

Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures. A signature is a characteristic byte-pattern that is part of a certain virus or family of viruses. If a virus scanner finds such a pattern in a file, it notifies the user that the file is infected. The user can then delete, or (in some cases) “clean” or “heal” the infected file. Some viruses employ techniques that make detection by means of signatures difficult but probably not impossible. These viruses modify their code on each infection. That is, each infected file contains a different variant of the virus.

Encryption with a variable key

A more advanced method is the use of simple encryption to encipher the virus. In this case, the virus consists of a small decrypting module and an encrypted copy of the virus code. If the virus is encrypted with a different key for each infected file, the only part of the virus that remains constant is the decrypting module, which would (for example) be appended to the end. In this case, a virus scanner cannot directly detect the virus using signatures, but it can still detect the decrypting module, which still makes indirect detection of the virus possible. Since these would be symmetric keys, stored on the infected host, it is in fact entirely possible to decrypt the final virus, but that probably isn’t required, since self-modifying code is such a rarity that it may be reason for virus scanners to at least flag the file as suspicious.

An old, but compact, encryption involves XORing each byte in a virus with a constant, so that the exclusive-or operation had only to be repeated for decryption. It is suspicious code that modifies itself, so the code to do the encryption/decryption may be part of the signature in many virus definitions.

Polymorphic code

Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures. Anti-virus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body. See Polymorphic code for technical detail on how such engines operate.[12]

Some viruses employ polymorphic code in a way that constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for anti-virus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that some instances of the virus may be able to avoid detection.

Metamorphic code

To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. Viruses that use this technique are said to be metamorphic. To enable metamorphism, a metamorphic engine is needed. A metamorphic virus is usually very large and complex. For example, W32/Simile consisted of over 14000 lines of Assembly language code, 90% of which is part of the metamorphic engine.[13][14]

Vulnerability and countermeasures The vulnerability of operating systems to viruses

Just as genetic diversity in a population decreases the chance of a single disease wiping out a population, the diversity of software systems on a network similarly limits the destructive potential of viruses.

This became a particular concern in the 1990s, when Microsoft gained market dominance in desktop operating systems and office suites. The users of Microsoft software (especially networking software such as Microsoft Outlook and Internet Explorer) are especially vulnerable to the spread of viruses. Microsoft software is targeted by virus writers due to their desktop dominance, and is often criticized for including many errors and holes for virus writers to exploit. Integrated and non-integrated Microsoft applications (such as Microsoft Office) and applications with scripting languages with access to the file system (for example Visual Basic Script (VBS), and applications with networking features) are also particularly vulnerable.

Although Windows is by far the most popular operating system for virus writers, some viruses also exist on other platforms. Any operating system that allows third-party programs to run can theoretically run viruses. Some operating systems are less secure than others. Unix-based OS’s (and NTFS-aware applications on Windows NT based platforms) only allow their users to run executables within their own protected memory space.

An Internet based research revealed that there were cases when people willingly pressed a particular button to download a virus. Security analyst Didier Stevens ran a half year advertising campaign on Google AdWords which said “Is your PC virus-free? Get it infected here!”. The result was 409 clicks.[15][16]

As of 2006[update], there are relatively few security exploits targeting Mac OS X (with a Unix-based file system and kernel).[17] The number of viruses for the older Apple operating systems, known as Mac OS Classic, varies greatly from source to source, with Apple stating that there are only four known viruses, and independent sources stating there are as many as 63 viruses. Virus vulnerability between Macs and Windows is a chief selling point, one that Apple uses in their Get a Mac advertising.[18] In January 2009, Symantec announced discovery of a trojan that targets Macs.[19] This discovery did not gain much coverage until April 2009.[19]

Windows and Unix have similar scripting abilities, but while Unix natively blocks normal users from having access to make changes to the operating system environment, older copies of Windows such as Windows 95 and 98 do not. In 1997, when a virus for Linux was released – known as “Bliss” – leading antivirus vendors issued warnings that Unix-like systems could fall prey to viruses just like Windows.[20] The Bliss virus may be considered characteristic of viruses – as opposed to worms – on Unix systems. Bliss requires that the user run it explicitly (so it is a trojan), and it can only infect programs that the user has the access to modify. Unlike Windows users, most Unix users do not log in as an administrator user except to install or configure software; as a result, even if a user ran the virus, it could not harm their operating system. The Bliss virus never became widespread, and remains chiefly a research curiosity. Its creator later posted the source code to Usenet, allowing researchers to see how it worked.[21]

The role of software development

Because software is often designed with security features to prevent unauthorized use of system resources, many viruses must exploit software bugs in a system or application to spread. Software development strategies that produce large numbers of bugs will generally also produce potential exploits.

Anti-virus software and other preventive measures

Many users install anti-virus software that can detect and eliminate known viruses after the computer downloads or runs the executable. There are two common methods that an anti-virus software application uses to detect viruses. The first, and by far the most common method of virus detection is using a list of virus signature definitions. This works by examining the content of the computer’s memory (its RAM, and boot sectors) and the files stored on fixed or removable drives (hard drives, floppy drives), and comparing those files against a database of known virus “signatures”. The disadvantage of this detection method is that users are only protected from viruses that pre-date their last virus definition update. The second method is to use a heuristic algorithm to find viruses based on common behaviors. This method has the ability to detect viruses that anti-virus security firms have yet to create a signature for.

Some anti-virus programs are able to scan opened files in addition to sent and received e-mails ‘on the fly’ in a similar manner. This practice is known as “on-access scanning.” Anti-virus software does not change the underlying capability of host software to transmit viruses. Users must update their software regularly to patch security holes. Anti-virus software also needs to be regularly updated in order to prevent the latest threats.

One may also minimise the damage done by viruses by making regular backups of data (and the Operating Systems) on different media, that are either kept unconnected to the system (most of the time), read-only or not accessible for other reasons, such as using different file systems. This way, if data is lost through a virus, one can start again using the backup (which should preferably be recent).

If a backup session on optical media like CD and DVD is closed, it becomes read-only and can no longer be affected by a virus (so long as a virus or infected file was not copied onto the CD/DVD). Likewise, an operating system on a bootable CD can be used to start the computer if the installed operating systems become unusable. Backups on removable media must be carefully inspected before restoration. The Gammima virus, for example, propagates via removable flash drives.[22][23]

Another method is to use different operating systems on different file systems. A virus is not likely to affect both. Data backups can also be put on different file systems. For example, Linux requires specific software to write to NTFS partitions, so if one does not install such software and uses a separate installation of MS Windows to make the backups on an NTFS partition, the backup should remain safe from any Linux viruses (unless they are written to specifically provide this capability). Likewise, MS Windows can not read file systems like ext3, so if one normally uses MS Windows, the backups can be made on an ext3 partition using a Linux installation.

Recovery methods

Once a computer has been compromised by a virus, it is usually unsafe to continue using the same computer without completely reinstalling the operating system. However, there are a number of recovery options that exist after a computer has a virus. These actions depend on severity of the type of virus.

Virus removal

One possibility on Windows Me, Windows XP and Windows Vista is a tool known as System Restore, which restores the registry and critical system files to a previous checkpoint. Often a virus will cause a system to hang, and a subsequent hard reboot will render a system restore point from the same day corrupt. Restore points from previous days should work provided the virus is not designed to corrupt the restore files or also exists in previous restore points.[24] Some viruses, however, disable system restore and other important tools such as Task Manager and Command Prompt. An example of a virus that does this is CiaDoor.

Administrators have the option to disable such tools from limited users for various reasons (for example, to reduce potential damage from and the spread of viruses). The virus modifies the registry to do the same, except, when the Administrator is controlling the computer, it blocks all users from accessing the tools. When an infected tool activates it gives the message “Task Manager has been disabled by your administrator.”, even if the user trying to open the program is the administrator.[citation needed]

Users running a Microsoft operating system can access Microsoft’s website to run a free scan, provided they have their 20-digit registration number.

Operating system reinstallation

Reinstalling the operating system is another approach to virus removal. It involves simply reformatting the OS partition and installing the OS from its original media, or imaging the partition with a clean backup image (Taken with Ghost or Acronis for example).

This method has the benefits of being simple to do, being faster than running multiple antivirus scans, and is guaranteed to remove any malware. Downsides include having to reinstall all other software, reconfiguring, restoring user preferences. User data can be backed up by booting off of a Live CD or putting the hard drive into another computer and booting from the other computer’s operating system (though care must be taken not

 

 

 

 

 

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or devour files on a targeted computer

 

Payloads

Many worms that have been created are only designed to spread, and don’t attempt to alter the systems they pass through. However, as the Morris worm and Mydoom showed, the network traffic and other unintended effects can often cause major disruption. A “payload” is code designed to do more than spread the worm – it might delete files on a host system (e.g., the ExploreZip worm), encrypt files in a cryptoviral extortion attack, or send documents via e-mail. A very common payload for worms is to install a backdoor in the infected computer to allow the creation of a “zombie” computer under control of the worm author – Sobig and Mydoom are examples which created zombies. Networks of such machines are often referred to as botnets and are very commonly used by spam senders for sending junk email or to cloak their website’s address.[1] Spammers are therefore thought to be a source of funding for the creation of such worms,[2][3] and the worm writers have been caught selling lists of IP addresses of infected machines.[4] Others try to blackmail companies with threatened DoS attacks.[5]

Backdoors can be exploited by other malware, including worms. Examples include Doomjuice, which spreads better using the backdoor opened by Mydoom, and at least one instance of malware taking advantage of the rootkit and backdoor installed by the Sony/BMG DRM software utilized by millions of music CDs prior to late 2005.

Worms with good intent

Beginning with the very first research into worms at Xerox PARC there have been attempts to create useful worms. The Nachi family of worms, for example, tried to download and install patches from Microsoft’s website to fix vulnerabilities in the host system – by exploiting those same vulnerabilities. In practice, although this may have made these systems more secure, it generated considerable network traffic, rebooted the machine in the course of patching it, and did its work without the consent of the computer’s owner or user.

Some worms, such as XSS worms, have been written for research to determine the factors of how worms spread, such as social activity and change in user behavior, while other worms are little more than a prank, such as one that sends the popular image macro of an owl with the phrase “O RLY?” to a print queue in the infected computer.

Most security experts regard all worms as malware, whatever their payload or their writers’ intentions

Protecting against dangerous computer worms

Worms spread by exploiting vulnerabilities in operating systems. All vendors supply regular security updates and if these are installed to a machine then the majority of worms are unable to spread to it. If a vendor acknowledges a vulnerability, but has yet to release a security update to patch it, a zero day exploit is possible. However, these are relatively rare.

Users need to be wary of opening unexpected email, and should not run attached files or programs, or visit web sites that are linked to such emails. However, as with the ILOVEYOU worm, and with the increased growth and efficiency of phishing attacks, it remains possible to trick the end-user into running a malicious code.

Anti-virus and anti-spyware software are helpful, but must be kept up-to-date with new pattern files at least every few days. The use of a firewall is also recommended.

In the April-June, 2008, issue of IEEE Transactions on Dependable and Secure Computing, computer scientists describe a potential new way to combat internet worms. The researchers discovered how to contain the kind of worm that scans the Internet randomly, looking for vulnerable hosts to infect. They found that the key is for software to monitor the number of scans that machines on a network sends out. When a machine starts sending out too many scans, it is a sign that it has been infected, allowing administrators to take it off line and check it for viruses

A Trojan horse, or trojan for short, is a term used to describe malware that appears, to the user, to perform a desirable function but, in fact, facilitates unauthorized access to the user’s computer system. The term comes from the Trojan Horse story in Greek mythology. Trojan horses are not self-replicating which distinguishes them from viruses and worms. Additionally, they require interaction with a hacker to fulfil their purpose. The hacker need not be the individual responsible for distributing the Trojan horse. It is possible for hackers to scan computers on a network using a port scanner in the hope of finding one with a Trojan horse installed

Purpose of Trojan horses

Trojan horses are designed to allow a hacker remote access to a target computer system. Once a Trojan horse has been installed on a target computer system it is possible for a hacker to access it remotely and perform operations. The type of operations that a hacker can perform are limited by user privileges on the target computer system and the design of the Trojan horse itself.

Operations which could be performed by a hacker on a target computer system include:

Deletion of files Modification of files Uploading of files Downloading of files Installation of software (including other malware) Data Theft (e.g. passwords, security codes, credit card information) Use of the machine as part of a Botnet (e.g. to perform Distributed Denial-of-service (DDoS) attacks) Keystroke logging Viewing the user’s screen

An example of a Trojan horse attack is one that was reported in 1999:

This Trojan horse was distributed using email. Reports suggest that it was widely distributed and that there were several versions. The email sent to distribute the Trojan horse purported to be from Microsoft Corporation and to offer a free upgrade for Microsoft Internet Explorer. The email did not originate from Microsoft Corporation nor did it provide an upgrade for Microsoft Internet Explorer. The Trojan horse was an executable file named “ie0199.exe” and was provided as an email attachment. One version of the email included the message:

As an user of the Microsoft Internet Explorer, Microsoft Corporation provides you with this upgrade for your web browser. It will fix some bugs found in your Internet Explorer. To install the upgrade, please save the attached file (ie0199.exe) in some folder and run it.

Once installed the Trojan horse reportedly modified system files and attempted to initiate contact with other remote systems.

Installation Software downloads (e.g. A Trojan horse included as part of a software application downloaded from File sharing networks) Websites containing executable content (e.g. A Trojan horse in the form of an ActiveX control) Email attachments Application exploits (Flaws in a web browser, media player, messaging client or other software which can be exploited to allow installation of a Trojan horse) Social Engineering (e.g. A hacker tricking a user into installing a Trojan horse by communicating with them directly)

Additionally, there have been reports of compilers which are themselves Trojan horses. In addition to compiling code to executable form they also insert code into the output executables which cause them to become Trojan horses. This is still distinct from self-replication as the process is not automatic.

Removal

Antivirus software is designed to detect and delete Trojan horses ideally preventing them from ever being installed. It may be possible to remove a Trojan horse manually given a full understanding of how that particular Trojan horse operates, however if it is possible that a Trojan horse has been used by a hacker to access a computer system it will be difficult to know what damage has been done and what other problems have been introduced. In situations where the security of the computer system is critical it is advisable to rebuild it from known good software

 

, created in 1986 by the Farooq Alvi Brothers, operating out of Lahore, Pakistan. The brothers reportedly created the virus to deter pirated copies of software they had written. However, analysts have claimed that the Ashar virus, a variant of Brain, possibly predated it based on code within the virus

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. PCs of the era would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the wild for many years.

Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS, modem use, and software sharing. Bulletin board-driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBS’s. Within the “pirate scene” of hobbyists trading illicit copies of retail software, traders in a hurry to obtain the latest applications were easy targets for viruses.

Macro viruses have become common since the mid-1990s. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel and spread throughout Microsoft Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS, most could also spread to Macintosh computers. Although most of these viruses did not have the ability to send infected e-mail, those viruses which did took advantage of the Microsoft Outlook COM interface. Some old versions of Microsoft Word allow macros to replicate themselves with additional blank lines. If two macro viruses simultaneously infect a document, the combination of the two, if also self-replicating, can appear as a “mating” of the two and would likely be detected as a virus unique from the “parents.”

A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating.

Cross-site scripting viruses emerged recently, and were academically demonstrated in 2005. Since 2005 there have been multiple instances of the cross-site scripting viruses in the wild, exploiting websites such as My Space, facebook and Yahoo.

Infection strategies

In order to replicate itself, a virus must be permitted to execute code and write to memory. For this reason, many viruses attach themselves to executable files that may be part of legitimate programs. If a user attempts to launch an infected program, the virus’ code may be executed simultaneously. Viruses can be divided into two types based on their behavior when they are executed. Nonresident viruses immediately search for other hosts that can be infected, infect those targets, and finally transfer control to the application program they infected. Resident viruses do not search for hosts when they are started. Instead, a resident virus loads itself into memory on execution and transfers control to the host program. The virus stays active in the background and infects new hosts when those files are accessed by other programs or the operating system itself.

Nonresident viruses

Nonresident viruses can be thought of as consisting of a finder module and a replication module. The finder module is responsible for finding new files to infect. For each new executable file the finder module encounters, it calls the replication module to infect that file.[11]

Resident viruses

Resident viruses contain a replication module that is similar to the one that is employed by nonresident viruses. This module, however, is not called by a finder module. The virus loads the replication module into memory when it is executed instead and ensures that this module is executed each time the operating system is called to perform a certain operation. the replication module can be called, for example, each time the operating system executes a file. In this case the virus infects every suitable program that is executed on the computer.

Resident viruses are sometimes subdivided into a category of fast infectors and a category of slow infectors. Fast infectors are designed to infect as many files as possible. A fast infector, for instance, can infect every potential host file that is accessed. This poses a special problem when using anti-virus software, since a virus scanner will access every potential host file on a computer when it performs a system-wide scan. If the virus scanner fails to notice that such a virus is present in memory the virus can “piggy-back” on the virus scanner and in this way infect all files that are scanned. Fast infectors rely on their fast infection rate to spread. The disadvantage of this method is that infecting many files may make detection more likely, because the virus may slow down a computer or perform many suspicious actions that can be noticed by anti-virus software. Slow infectors, on the other hand, are designed to infect hosts infrequently. Some slow infectors, for instance, only infect files when they are copied. Slow infectors are designed to avoid detection by limiting their actions: they are less likely to slow down a computer noticeably and will, at most, infrequently trigger anti-virus software that detects suspicious behavior by programs. The slow infector approach, however, does not seem very successful.

Vectors and hosts

Viruses have targeted various types of transmission media or hosts. This list is not exhaustive:

Binary executable files (such as COM files and EXE files in MS-DOS, Portable Executable files in Microsoft Windows, and ELF files in Linux) Volume Boot Records of floppy disks and hard disk partitions The master boot record (MBR) of a hard disk General-purpose script files (such as batch files in MS-DOS and Microsoft Windows, VBScript files, and shell script files on Unix-like platforms). Application-specific script files (such as Telix-scripts) System specific autorun script files (such as Autorun.inf file needed to Windows to automatically run software stored on USB Memory Storage Devices). Documents that can contain macros (such as Microsoft Word documents, Microsoft Excel spreadsheets, AmiPro documents, and Microsoft Access database files) Cross-site scripting vulnerabilities in web applications Arbitrary computer files. An exploitable buffer overflow, format string, race condition or other exploitable bug in a program which reads the file could be used to trigger the execution of code hidden within it. Most bugs of this type can be made more difficult to exploit in computer architectures with protection features such as an execute disable bit and/or address space layout randomization.

PDFs, like HTML, may link to malicious code.[citation needed]PDFs can also be infected with malicious code.

In operating systems that use file extensions to determine program associations (such as Microsoft Windows), the extensions may be hidden from the user by default. This makes it possible to create a file that is of a different type than it appears to the user. For example, an executable may be created named “picture.png.exe”, in which the user sees only “picture.png” and therefore assumes that this file is an image and most likely is safe.

An additional method is to generate the virus code from parts of existing operating system files by using the CRC16/CRC32 data. The initial code can be quite small (tens of bytes) and unpack a fairly large virus. This is analogous to a biological “prion” in the way it works but is vulnerable to signature based detection.

This attack has not yet been seen “in the wild”.

Methods to avoid detection

In order to avoid detection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the “last modified” date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.

Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.

Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.

As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access.

Avoiding bait files and other undesirable hosts

A virus needs to infect hosts in order to spread further. In some cases, it might be a bad idea to infect a host program. For example, many anti-virus programs perform an integrity check of their own code. Infecting such programs will therefore increase the likelihood that the virus is detected. For this reason, some viruses are programmed not to infect programs that are known to be part of anti-virus software. Another type of host that viruses sometimes avoid is bait files. Bait files (or goat files) are files that are specially created by anti-virus software, or by anti-virus professionals themselves, to be infected by a virus. These files can be created for various reasons, all of which are related to the detection of the virus:

Anti-virus professionals can use bait files to take a sample of a virus (i.e. a copy of a program file that is infected by the virus). It is more practical to store and exchange a small, infected bait file, than to exchange a large application program that has been infected by the virus. Anti-virus professionals can use bait files to study the behavior of a virus and evaluate detection methods. This is especially useful when the virus is polymorphic. In this case, the virus can be made to infect a large number of bait files. The infected files can be used to test whether a virus scanner detects all versions of the virus. Some anti-virus software employs bait files that are accessed regularly. When these files are modified, the anti-virus software warns the user that a virus is probably active on the system.

Since bait files are used to detect the virus, or to make detection possible, a virus can benefit from not infecting them. Viruses typically do this by avoiding suspicious programs, such as small program files or programs that contain certain patterns of ‘garbage instructions’.

A related strategy to make baiting difficult is sparse infection. Sometimes, sparse infectors do not infect a host file that would be a suitable candidate for infection in other circumstances. For example, a virus can decide on a random basis whether to infect a file or not, or a virus can only infect host files on particular days of the week.

Stealth

Some viruses try to trick anti-virus software by intercepting its requests to the operating system. A virus can hide itself by intercepting the anti-virus software’s request to read the file and passing the request to the virus, instead of the OS. The virus can then return an uninfected version of the file to the anti-virus software, so that it seems that the file is “clean”. Modern anti-virus software employs various techniques to counter stealth mechanisms of viruses. The only completely reliable method to avoid stealth is to boot from a medium that is known to be clean.

Self-modification

Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures. A signature is a characteristic byte-pattern that is part of a certain virus or family of viruses. If a virus scanner finds such a pattern in a file, it notifies the user that the file is infected. The user can then delete, or (in some cases) “clean” or “heal” the infected file. Some viruses employ techniques that make detection by means of signatures difficult but probably not impossible. These viruses modify their code on each infection. That is, each infected file contains a different variant of the virus.

Encryption with a variable key

A more advanced method is the use of simple encryption to encipher the virus. In this case, the virus consists of a small decrypting module and an encrypted copy of the virus code. If the virus is encrypted with a different key for each infected file, the only part of the virus that remains constant is the decrypting module, which would (for example) be appended to the end. In this case, a virus scanner cannot directly detect the virus using signatures, but it can still detect the decrypting module, which still makes indirect detection of the virus possible. Since these would be symmetric keys, stored on the infected host, it is in fact entirely possible to decrypt the final virus, but that probably isn’t required, since self-modifying code is such a rarity that it may be reason for virus scanners to at least flag the file as suspicious.

An old, but compact, encryption involves XORing each byte in a virus with a constant, so that the exclusive-or operation had only to be repeated for decryption. It is suspicious code that modifies itself, so the code to do the encryption/decryption may be part of the signature in many virus definitions.

Polymorphic code

Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures. Anti-virus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body. See Polymorphic code for technical detail on how such engines operate.[12]

Some viruses employ polymorphic code in a way that constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for anti-virus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that some instances of the virus may be able to avoid detection.

Metamorphic code

To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. Viruses that use this technique are said to be metamorphic. To enable metamorphism, a metamorphic engine is needed. A metamorphic virus is usually very large and complex. For example, W32/Simile consisted of over 14000 lines of Assembly language code, 90% of which is part of the metamorphic engine.[13][14]

Vulnerability and countermeasures The vulnerability of operating systems to viruses

Just as genetic diversity in a population decreases the chance of a single disease wiping out a population, the diversity of software systems on a network similarly limits the destructive potential of viruses.

This became a particular concern in the 1990s, when Microsoft gained market dominance in desktop operating systems and office suites. The users of Microsoft software (especially networking software such as Microsoft Outlook and Internet Explorer) are especially vulnerable to the spread of viruses. Microsoft software is targeted by virus writers due to their desktop dominance, and is often criticized for including many errors and holes for virus writers to exploit. Integrated and non-integrated Microsoft applications (such as Microsoft Office) and applications with scripting languages with access to the file system (for example Visual Basic Script (VBS), and applications with networking features) are also particularly vulnerable.

Although Windows is by far the most popular operating system for virus writers, some viruses also exist on other platforms. Any operating system that allows third-party programs to run can theoretically run viruses. Some operating systems are less secure than others. Unix-based OS’s (and NTFS-aware applications on Windows NT based platforms) only allow their users to run executables within their own protected memory space.

An Internet based research revealed that there were cases when people willingly pressed a particular button to download a virus. Security analyst Didier Stevens ran a half year advertising campaign on Google AdWords which said “Is your PC virus-free? Get it infected here!”. The result was 409 clicks.[15][16]

As of 2006[update], there are relatively few security exploits targeting Mac OS X (with a Unix-based file system and kernel).[17] The number of viruses for the older Apple operating systems, known as Mac OS Classic, varies greatly from source to source, with Apple stating that there are only four known viruses, and independent sources stating there are as many as 63 viruses. Virus vulnerability between Macs and Windows is a chief selling point, one that Apple uses in their Get a Mac advertising.[18] In January 2009, Symantec announced discovery of a trojan that targets Macs.[19] This discovery did not gain much coverage until April 2009.[19]

Windows and Unix have similar scripting abilities, but while Unix natively blocks normal users from having access to make changes to the operating system environment, older copies of Windows such as Windows 95 and 98 do not. In 1997, when a virus for Linux was released – known as “Bliss” – leading antivirus vendors issued warnings that Unix-like systems could fall prey to viruses just like Windows.[20] The Bliss virus may be considered characteristic of viruses – as opposed to worms – on Unix systems. Bliss requires that the user run it explicitly (so it is a trojan), and it can only infect programs that the user has the access to modify. Unlike Windows users, most Unix users do not log in as an administrator user except to install or configure software; as a result, even if a user ran the virus, it could not harm their operating system. The Bliss virus never became widespread, and remains chiefly a research curiosity. Its creator later posted the source code to Usenet, allowing researchers to see how it worked.[21]

The role of software development

Because software is often designed with security features to prevent unauthorized use of system resources, many viruses must exploit software bugs in a system or application to spread. Software development strategies that produce large numbers of bugs will generally also produce potential exploits.

Anti-virus software and other preventive measures

Many users install anti-virus software that can detect and eliminate known viruses after the computer downloads or runs the executable. There are two common methods that an anti-virus software application uses to detect viruses. The first, and by far the most common method of virus detection is using a list of virus signature definitions. This works by examining the content of the computer’s memory (its RAM, and boot sectors) and the files stored on fixed or removable drives (hard drives, floppy drives), and comparing those files against a database of known virus “signatures”. The disadvantage of this detection method is that users are only protected from viruses that pre-date their last virus definition update. The second method is to use a heuristic algorithm to find viruses based on common behaviors. This method has the ability to detect viruses that anti-virus security firms have yet to create a signature for.

Some anti-virus programs are able to scan opened files in addition to sent and received e-mails ‘on the fly’ in a similar manner. This practice is known as “on-access scanning.” Anti-virus software does not change the underlying capability of host software to transmit viruses. Users must update their software regularly to patch security holes. Anti-virus software also needs to be regularly updated in order to prevent the latest threats.

One may also minimise the damage done by viruses by making regular backups of data (and the Operating Systems) on different media, that are either kept unconnected to the system (most of the time), read-only or not accessible for other reasons, such as using different file systems. This way, if data is lost through a virus, one can start again using the backup (which should preferably be recent).

If a backup session on optical media like CD and DVD is closed, it becomes read-only and can no longer be affected by a virus (so long as a virus or infected file was not copied onto the CD/DVD). Likewise, an operating system on a bootable CD can be used to start the computer if the installed operating systems become unusable. Backups on removable media must be carefully inspected before restoration. The Gammima virus, for example, propagates via removable flash drives.[22][23]

Another method is to use different operating systems on different file systems. A virus is not likely to affect both. Data backups can also be put on different file systems. For example, Linux requires specific software to write to NTFS partitions, so if one does not install such software and uses a separate installation of MS Windows to make the backups on an NTFS partition, the backup should remain safe from any Linux viruses (unless they are written to specifically provide this capability). Likewise, MS Windows can not read file systems like ext3, so if one normally uses MS Windows, the backups can be made on an ext3 partition using a Linux installation.

Recovery methods

Once a computer has been compromised by a virus, it is usually unsafe to continue using the same computer without completely reinstalling the operating system. However, there are a number of recovery options that exist after a computer has a virus. These actions depend on severity of the type of virus.

Virus removal

One possibility on Windows Me, Windows XP and Windows Vista is a tool known as System Restore, which restores the registry and critical system files to a previous checkpoint. Often a virus will cause a system to hang, and a subsequent hard reboot will render a system restore point from the same day corrupt. Restore points from previous days should work provided the virus is not designed to corrupt the restore files or also exists in previous restore points.[24] Some viruses, however, disable system restore and other important tools such as Task Manager and Command Prompt. An example of a virus that does this is CiaDoor.

Administrators have the option to disable such tools from limited users for various reasons (for example, to reduce potential damage from and the spread of viruses). The virus modifies the registry to do the same, except, when the Administrator is controlling the computer, it blocks all users from accessing the tools. When an infected tool activates it gives the message “Task Manager has been disabled by your administrator.”, even if the user trying to open the program is the administrator.[citation needed]

Users running a Microsoft operating system can access Microsoft’s website to run a free scan, provided they have their 20-digit registration number.

Operating system reinstallation

Reinstalling the operating system is another approach to virus removal. It involves simply reformatting the OS partition and installing the OS from its original media, or imaging the partition with a clean backup image (Taken with Ghost or Acronis for example).

This method has the benefits of being simple to do, being faster than running multiple antivirus scans, and is guaranteed to remove any malware. Downsides include having to reinstall all other software, reconfiguring, restoring user preferences. User data can be backed up by booting off of a Live CD or putting the hard drive into another computer and booting from the other computer’s operating system (though care must be taken not

 

 

 

 

 

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or devour files on a targeted computer

 

Payloads

Many worms that have been created are only designed to spread, and don’t attempt to alter the systems they pass through. However, as the Morris worm and Mydoom showed, the network traffic and other unintended effects can often cause major disruption. A “payload” is code designed to do more than spread the worm – it might delete files on a host system (e.g., the ExploreZip worm), encrypt files in a cryptoviral extortion attack, or send documents via e-mail. A very common payload for worms is to install a backdoor in the infected computer to allow the creation of a “zombie” computer under control of the worm author – Sobig and Mydoom are examples which created zombies. Networks of such machines are often referred to as botnets and are very commonly used by spam senders for sending junk email or to cloak the

Computer Parts: A General Purpose Guide

Upon reviewing my knowledge of the Information Technology society, I discovered that we are too few. Actually we are to numerous by count of inexperienced “technicians,” to such a degree, that I have decided to begin writing an introductory article on computers and their components. In this article I will be detailing the primary components of a standard desktop and/or tower computer. The article you read now contains an explanation of key components, designed to provide an introduction to computers. If you know (or think you know) what the parts are already please do not waste your time reading this article as it will probably be quite redundant and boring to you. Over the course of the reading I will explain what motherboards, Processors, Power Supplies, Memory, hard drives, Solid State Drives, and expansion cards are, as well as what they do.

The motherboard (also known as the mainboard or mobo) is the foundation component that computers must have in order to do anything. Without this component your computer would not function. It wouldn’t even be a computer because it wouldn’t know what a function was to begin with. The motherboard comes in many forms, the most common of which are mini-ITX, ATX, and e-ATX. The board also houses various interfaces for many devices. Serial ATA (SATA) and ATA (commonly referred to as IDE) are the most commonly used device interfaces. There are also several sets of pins on the board for USB interfaces. These are clusters of pins are called “headers” and allow expansion. Also on the mainboard there is a set of plastic slots (generally located next to the CPU) for memory. In to the memory slots, you will find several different types of expansion card slots, such as PCI, PCI-e x1, and PCI-e x8 or x16. These expansion slots allow the user to later put in cards that can provide assorted functions in the as well as providing a foundation for computer. None of this matters without two other components, the first of which is the Processor.

Central Processing Units (also known as processors or CPU’s) are the brains of the whole operation. This component is the brain of the computer. In order to do anything your computer must have a properly installed CPU. When installing a CPU, make sure that you align notches on the chip itself with the notches on the CPU socket. This will ensure that you do not damage the CPU or motherboard. The next step is to install the heatsink and fan to cool the processor. When installing these cooling products you must use thermal compound. Thermal compound is a paste that transfers heat from the metal of the CPU to the metal of the heatsink. Without thermal compound a heatsink is useless. To install the heatsink, you first administer a small amount of thermal paste (via brush or syringe) onto the CPU. (It is very important not to get any thermal paste on the pin side of the CPU.) After applying thermal paste, you will align the heatsink with the plastic on the motherboard and then press down firmly. You are now ready to install the memory.

Random Access Memory (commonly referred to as RAM or memory) is another of the basic components necessary for a computer to function. When powered on without it, the computer will emit a series of three evenly spaced beeps and will not display anything on the screen. Memory consists of multiple sets of integrated circuit chips set into a circuit board. The gold leads at the bottom of the memory stick conduct electrical signals to the circuits and allow the computer to process information. Memory is volatile, meaning that it will not retain any data when power to the system is lost. Thus users should save their data often in order to retain it in the event of power loss. When installing memory make sure that you align the notches with the bump(s) in the memory slot. Also make sure that you have the right type of memory (DDR, DDR2, or DDR3).

Sometimes referred to as a PSU (Power Supply Unit), the power supply is a metal box containing capacitors and other electrical components that allow the computer to be powered from a simple wall socket. The power supply is responsible for drawing power from the wall socket and directing it to specific components in the computer.

The hard disk drive (HDD) is the part of the computer where files are stored. Hard Drive’s hold information on magnetic platters so that the data can be used later. Memory is volatile (not able to store data), but these drive’s are non-volatile. This is because instead of using constant electric currents, they use magnetic 1’s and 0’s to store the information. When choosing a hard drive, there a few options to consider. How much storage space is necessary? This is a question to consider due to the relatively large amount of data users typically process and store over the course of their lives (such as pictures or music). Usually bigger is better, but users probably won’t need to have a one terabyte hard drive. How fast does it need to spin? Again faster is better, but faster also equals more expensive. Higher rpm’s mean faster read/write speeds thus making the computer just that much faster. What about SSD’s? SSD’s (Solid State Drives) are a relatively new improvement to the data storage market. Considering their relative youth they are not necessarily going to be the best method of storage for the average user. They are currently geared more towards the enthusiast or gamer than the average PC user. They also cost more per gigabyte than the average hard drive due to their faster read/write speeds.

Optical disc drives (such as CD and DVD drives) are considered removable storage media devices. These devices make use of lasers for both reading and writing information to removable discs. The discs store information through pits in their reflective coating. As the disc spins, the optical drive projects invisible laser light to the disk, and receives the stored information through the deflected output. Writing or burning information to the disc is performed in much the same way except that the laser changes the way the pits on the disc are arranged.

Graphics cards are amongst the most commonly upgraded components of a computer. A graphics card has an onboard GPU (Graphics Processing Unit) and its own set of graphics memory. Modern graphics cards commonly use PCI express interface slots to communicate with the motherboard. Often times the high-end graphics cards require power directly from the power supply. Other lower-end graphics cards can simply be powered by the PCIe bus. There are two primary manufacturers of computer graphics cards: NVIDIA and ATI. These two companies have many great cards, and are constantly improving them. Before choosing a graphics card the user should consider what the primary use of their computer will be. Gaming computers generally need a mid-range to high-end graphics card. Computers that will be used for internet browsing and word-processing probably will not need a graphics card expansion.

Sound cards provide better quality sound and additional channels. Onboard sound cards have a microphone, audio in, and speaker/headphone ports. Expansion slot sound cards generally have four more ports for surround sound: right to left, rear stereo, subwoofer, and a MIDI/game port. The ports on the graphics cards are labeled as follows:

To sum up, there are many components required for a computer to function. Over the course of the reading I explained what motherboards, Processors, Power Supplies, Memory, hard drives, Solid State Drives, and expansion cards are, as well as what they do. I hope this article has been helpful to you.

Intel Extends Effort On Brain-Machine Interface

Thought controlled technology or brain–machine interface is the direct communication between a brain and an external device. The technology can assist, or repair human cognitive or sensory-motor functions. However, the technology is accompanied with serious objections about privacy violations and other possible abuses, various organizations are exploring its commercial potential.

Intel Corp, the world’s largest chipmaker has also joined the technological quest to allow people to operate computers, television sets and cell phones solely with their thoughts.

Intel joins the bandwagon

According to the Chipzilla, if developers could decipher the brain activity and patterns, then it can be possible to access the global information network simply by using thoughts, and it will open enormous new opportunities for computing technology.

Scientists have examined the brain’s electrical activity and flow of blood when people think about certain words and actions, and have identified patterns that PCs can be programmed to read. It would provide new possibility to a number of fascinating applications.

Recent Efforts

Recently, it has been demonstrated that persons suffering from severe ailments like paralysis have changed TV stations, turn on lights and write on a computer through brain-reading gadgets.

Similarly, Emotiv Systems of San Francisco has designed a headset, which can allow users to control video games by their thoughts rather by any joystick. Further, Honda had shown a robot whose arm can be mentally controlled by a person last year.

In the 2010 Winter Olympics at Vancouver, InteraXon’s Bright Ideas has demonstrated and also allowed people to switch on/off the lights at major Landmarks in Ontario using thought alone. It is one of the largest thought-controlled computing installations ever created.

Microsoft’s Project Natal

Nintendo, Japan based video game company has been offering its users to direct game action by waving the controller around through its Wii-mote since last year. For example, for a bowling action, gamer have to swing the Wii-mote in a bowling motion. On the similar path, Microsoft is working on Project Natal, its controller-free gaming and entertainment experience on the Xbox 360 video game platform.

The Project Natal comes with a sensor, which is about 9-inch wide horizontal bar and allows 3D motion sensing, facial and sound recognition of the players. The sensor features an RGB camera, depth sensor, microphone and required software.

The new application will work as an add-on for the Xbox 360 console and will allow users to manage or play games, movies or anything with their hands alone and without touching any hardware. It is different from what Intel is trying to do, but the concept is similar.

Discussion

If the chipmaker succeed in developing thought-controlled technology, it could be beneficial to mankind as well as military applications. Hence, there is need for the judicious use of the technology and to respect users’ privacy, so that the technology could not go into the hands of evil.

Computer Peripherals ? to Accelerate the Performance of Your Pc

Computer peripheral is a term that is sometimes referred exclusively for devices that are connected externally, generally those that are connected through some form of computer bus like the USB. Its most common examples include joysticks, printers and scanners.

However in a mixed opinion, some people say, internal devices like the video capture cards are not really computer peripherals since they are added inside the computer case. In their opinion the term peripherals is exclusively reserved for devices that are hooked up externally to the computer. It is arguable however whether PCMCIA cards qualify as peripherals under this biased definition. Because there are some hard wares that go fully inside the laptop, while some others like WiFi cards, have external appendages.

Due to these deliberations, the term is hardly used these days. Earlier these were used to refer to things like floppy disk drives and modems. Now a day’s most of these devices are integrated inside the computer’s case. Over and above the external devices typically function on their own such as mp3 players and cell phones.

The common peripherals include.

• Storage: CD, CD ROM, CD writer, DVD, DVD ROM, DVD writer, HD DVD, HD DVD ROM, HD DVD Writer, etc. Other examples in this category include USB flash drive, tape drive, floppy disk, and punch card. In the non removable category are the disk drives, disk array controller, etc.

• Input: In this category devices like keyboard, pointing devices, mouse, trackball, joystick, touch screen, game pad are included.

The devices like the power cord/ transformer, microphone, brain computer interface, image scanner, computer terminal, computer speech recognition, webcam, digitizing tablet, barcode reader are also included in this category.

• Output: For the printing purposes the devices that are used like the plotter, printer, Braille embosser, etc, the devices for the sound like the computer speech synthesis, sound card, speakers, etc are the output peripherals.

The devices for the visuals like the digital camera, graphics card, monitor, the devices for networking like the modem and the network card, expansion devices like the docking station, etc are other output peripheral devices.

Many online computer shopping, portals are giving discount on every purchase of computer peripheral item.