McAfee FreeScan
mcAfee FreeScan helps you detect thousands of viruses on your computer.

Symantec Security Check
Test your computer's exposure to online security threats and learn how to make your computer more secure.

Trend Micro^TM  HouseCall
Trend Micro^TM HouseCall^TM  is a FREE Web-based solution designed to scan your PC for a wide range of Internet security threats including viruses,worms,Trojans and spyware.