AVG AntiVirus is a great free AntiVirus program. They do have a for pay version, but I doubt that many home users will need it. Personally I use the AVG Antivirus Free edition on my on PC (Windows Vista) and it works very well.

You can can find the freedownload at AVG AntiVirus’ website.

Installation is fast and simple. Be sure to remove any other antivirus software you may have on your computer already though.