Online Anti-Virus Scanners
What do you do when your Anti-Virus has been trashed and the malware you are using constantly is redirecting you to different sites every time you try to re-download an anti-virus package? There are "free" online scanners that can be used in a "one off" fashion. I would normally recommend running these in Safe Mode W/Networking.
GFI's Vipre LIVE Checker
Mcafee's Stinger
Symantec's Free Virus Scan
Microsoft's Free OnLine Scanner
Panda's Free Online Scanner
Trend Micro's House Call Scanner
Bit Defender's Online Scanner
Eset's Online Scanner
F-Secure's Online Scanner