ali: If you have money to purchase something, I VERY HIGHLY recommend Trend Micro PC-cillin Internet Security.

Trend Site: http://www.trendmicro.com

PC-cillin site: http://www.trendmicro.com/en/products/desktop/pc-cillin/evaluate/overview.htm

Plus I'm not sure if this is still valid or not since it still says version 2005 on this page (2006 is current version), but it allows you to get 50% off the price. (So instead of around $50, it would be around $25): http://www.trendmicro.com/offers/ms-wsc/english.asp

Not only is it an anti-virus, but also a firewall, spam filter, spyware protection, etc... I love it. New updates for it almost daily (which it will find & update itself), and never had any problems with viruses/spyware getting on my PC while I had this loaded.