good tools to have around: Adaware VX2 plugin/extension/tool.
Also, HijackThis! in safe mode (f8 during boot, NO networking), can solve a TON of problems (as well as adaware, spybot, and norton AV in safe mode)
Also check your services (assuming 2000/XP) for anything out of the ordinary. (and stop/disable as needed. -- Messenger (not MSN messenger, talking about the "Messenger" service here) is usually a good idea to disable on "home" PCs--as well as "remote registry service")
Spent a good bit this weekend destroying viruses/spyware on my family's machines, so it's a little fresh--and makes me shudder 😃