This is a list of the best free tools I've found to get your computer virus free. Everything here is legit, malware free and none of that free scan but, then you gotta pay to clean crap either! When you're done here check out the security page for some free options to keep you protected.
HouseCall - Full-featured scan provided by TrendMicro, IMHO one of the better companys in the business.
Kaspersky Lab - Complete and quality scan, particularly light-weight..
ESET Online Scanner - From the maker of the popular NOD32 products.
OneCare Safety Scanner - Microsoft Windows Live security scan.
CWShredder - Removes CoolWebSearch browser hijackers. 9.x, 2000, XP
HijackThis - Scans your Windows computer to find settings that may have been changed by spyware, malware or other unwanted programs. For the more advanced user. 9.x, 2000, XP, Vista
Malicious Software Removal Tool - Provided by Microsoft for XP and up. Runs in the background automatically and targets specific, prevalent malware.
Malwarebytes' Anti-Malware - One of the best free anti-malware apps out there. 2000, XP, Vista
RKill - Stops malicious processes from running so that they can be removed manually or via application such as Malwarebytes.
Trojan Remover - Only free for 30 days but, included here because it's helped me to get rid of some hard to remove worms & trojans. 9.x, 2000, XP, Vista