:: Anti-Virus
Good anti-virus software is a must-have for any Windows user. I would avoid Norton Antivirus. It ranked very poorly against other packages (even some of the free ones), and was ranked worst for slowing down your computer. Also check out Virus Bulletin for independent rankings. You should never run more than one antivirus software.
NOD32 Anti-Virus
Leo Laporte raves about NOD32 Anti-Virus from eset. It's a solid, non-intrusive anti-virus application with heuristic testing, meaning it can even catch unknown viruses. It comes highly recommended. If you're going to buy anti-virus software, this is the one to buy.
Website: http://www.eset.com/products/windows.php
Price: $39
AOL Active Virus Shield
Active Virus Shield is actually a version of Kaspersky Antivirus (ranked #1). The only controversy over this product is that it periodically gathers and sends usage data back to AOL. Also, you agree to permit AOL's affiliates to send you e-mail.
Download Link: [Download]
Price: Free
avast! Home Edition
From lifehacker: " Slower but perhaps the most thorough for the worse-off machines. "
Company: alwil software
Download Link: [Download]
Price: Free
Avira AntiVir PersonalEdition Classic
AntiVir ranked high on a recent comparison.
Website: http://www.free-av.com
Price: Free
AVG Anti-Virus Free Edition
Grisoft puts out a good free anti-virus tool called AVG Anti-Virus Free Edition. AVG ranked lower on the list of free antivirus software, but it does have heuristic testing, meaning it can catch unknown viruses.
Company: Grisoft
Download Link: [Download]
Price: Free
ClamWin Free Antivirus
This opensource anti-virus software is probably the most unintrusive free anti-virus software out there.
Company: ClamWin
Download Link: [Download]
Price: Free
Trend Micro Free Online Virus Scan
Trend Micro also provides a free online scan.
Price: Free
RAV - Romanian AntiVirus
Microsoft has aquired GeCAD Software's antivirus technology. RAV is no longer being sold as a stand-alone product. However, they still offer a free online scan. It allows you to scan one file at a time.
Price: Free