Virus Protection
A virus can do real damage to your PC. It can delete files, disable features or trash your hard drive. Even a so called harmless virus presents a risk as it changes settings in the PC operating system which can cause problems.
Viruses really only affect computers running Windows, not other systems such as Mac and Linux.
Install virus protection
If you use Microsoft software, you need to have virus protection on your PC. There are plenty of options available, and you can read more here.
Virus Definitions
Most virus protection systems use a set of definitions to spot a virus. This means they can only find viruses that they know about. You need to keep the definition up to date so your PC is protected against the latest viruses.
Types
Well, there is only one type of virus - bad. But they do have some differences that are worth noting.
Virus - a programme that inserts itself in other programme files. When the infected programme runs, it activates the virus. The virus spreads when an infected file is copied to another PC.
Trojan - a programme that runs on your PC and performs functions for someone else, such as copy files, steal passwords or provide an entry point for a hacker. The trojan may do something, such as a screen saver, or it may be almost invisible to a user. A trojan does not replicate itself.
Worm - a self replicating programme. A worm can copy itself using email or a network, and can carry a destructive payload. More commonly, the damage done is through simply overloading computer networks as the worm replicates exponentially.
Recovery Disk
If your PC gets infected, you will need some tools to repair it. Many anti-virus software vendors provide a recovery disc for this job.
Some recovery disks need to be built specific for your system, in which case they should be updated every month or so, to be kept matched to your system.