Recommendations from sources I tend to trust; this isn't necessarily stuff I've tried personally.
Another free antivirus program is AVG, from Grisoft which I have used and helped others use.
F-Prot is an up to date DOS anti-virus program. You can boot your computer from a DOS floppy and run F-Prot.
To learn how to get rid of viruses, spyware, malware, Trojans and other scumware, start here
Select the Virus & Antivirus
Select the Parasites - Adware - Spyware and other scumware section: