Hijack This by Trend Micro

If persistent spyware is bogging down your computer, you might need HijackThis. The tiny program examines vulnerable or suspect parts of your system, such as browser helper objects and certain types of Registry keys. Pressing the Scan button generates a log of dozens of items, most of which are just customizations. Don't check off an item and hit the Fix Checked button unless you're sure it's malware. Clicking Info on Selected Item tells you why the entry was flagged as suspicious, but not whether it's actually malware. To find that out, search the Web for that item's name or go straight to a forum, such as SpywareInfo or Computer Cops. Saving the log creates a text document you can post to these forums.