Anti-virus software is used to find, remove or fix files that are infected with computer viruses. Most anti-virus companies release weekly updates of their databases to help keep you safe. Your anti-virus software uses these weekly updates (also known as virus signatures or definitions file) to identify newly discovered viruses.

The most basic anti-virus programs normally have several features to it, the memory resident scan, the system or file scan, and an automated updater. Many more sophisticated programs have many other integration tools that loan in to your instant messengers, your e-mail software and many other programs.

It's very important when you configure your anti-virus software to always make sure you can download new updates every week, if you scan your system for viruses, and your definitions file is out of date it may not even find a problem with your system. Additionally, you should make sure you do in fact scan your system on a regular basis. I personally set my computer to scan around 4 AM so it doesn't bother me.

When you download software, e-mail attachments, or introduce new media (diskettes, cd's, jump drives) in to your system you should scan them before running or viewing them inside another application.

Deciding on which program to use often causes people a lot of head aches. Some anti-virus programs require you to pay each year for a subscription to their virus databases so you can keep your system up to date, others are just expensive out of the box. Additionally, which tends to be the biggest factor in my decision making, is how much resources does the program use.

My favorite anti-virus program for the past couple of years is AVG Anti-Virus, by GriSoft. It's totally free for the personal edition and the updates as well. It has all the major features expected out of an anti-virus suite and is really simple to use and setup.

In the end, it doesn't really matter all that much which program you prefer, but it's very important that you do at least run one!