Ouchies. My comp runs AVG, Microsoft Beta, AdAware and Spybot and they seem to do the trick. Though if you don't have them, your obviously going to have to get on the net to get them, once again taking you back to square one. If all else fails, invest in a spare hard drive and reboot, pain in the butt but did it myself awhile ago on a non related matter and saved me a lot of heartbreak and frustration.
As UKBobby said, check out which folders and files have been created lately, make sure you have 'show all hidden files/folders' tabbed on.