What is a computer Virus?

A Computer virus is a computer program, that is able to infect other programs by modifying them, to include a version of itself. Viruses are not program errors or hardware malfunctions. Viruses can spread from computer to computer via Diskettes, Local Networks, or the Internet. In addition to replicating, some viruses can cause damage to data, corrupting programs, deleting files or overwriting your entire hard disk.

What is a Worm?
A computer WORM is a self-contained program (or set of programs), that is able to spread functional copies of itself or its segments to other computer systems (usually via network connections).
Note that unlike viruses, worms do not need to attach themselves to a host program. There are two types of worms--host computer worms and network worms.
What are the symptoms and indications of a virus infection?

There are various kinds of symptoms that some virus authors have written into their programs, such as messages, music and graphical displays. The main indications, however, are changes in file sizes and contents, changing of interrupt vectors, or the reassignment of other system resources. The unaccounted use of RAM or a reduction in the amount reported to be in the machine are important indicators. Examination of program code is valuable to the trained eye, but even a novice can often spot the gross differences between a valid boot sector and some viral ones. These symptoms, along with longer disk activity and strange behavior from the hardware, may instead be caused by genuine software, by harmless "joke" programs, or by hardware faults.

I got a Virus, How do I get remove it?

The key to removing any viruses is to ensure that it is not resident in memory. Although a lot of viruses can be removed manually, I suggest using a commercial AntiVirus product, such as Symantec�s Norton AntiVirus (http://www.symantec.com), whose repair routines are much safer and more reliable.
To get started, you will need a clean (non-infected) Boot Disk, (Preferably one created with the same Operating System as the infected computer), and an AntiVirus scanner. For the purpose of this discussion, I will use Norton AntiVirus as my scanner. If you do not have Norton AntiVirus, or any antiviral program, you can download the free Norton AntiVirus Command Line Scanner from http://www.symantec.com/nav/index_downloads.html. Scroll down the page to where it states free scanner. Double click the link to download, or click here to start downloading
To clean any virus, you need to reboot your computer so that the Virus is not in memory. To do this you will need to boot with a CLEAN (Non-Infected), Write Protected Boot Diskette. Once you have booted your computer you need to run Noron AntiVirus.
If a virus is still found in memory, one of two things is happening: the diskette is infected or the System Boot Sequence in the BIOS is set to bypass the floppy drive when booting. Many Viruses, once they are loaded into memory from the hard drive, will check the A: drive to see if it has a floppy diskette. If there is a floppy in the drive, the virus will transfer the boot sequence to the floppy diskette, giving the user the appearance that they did, in fact boot from the A: drive. In reality the system booted from the hard drive first, before continuing onto the A: drive. You will have to check your computers CMOS to see if you can change the boot sequence to a: only.