This site has an excellent scanner that will pick up just about any spyware that haunts your PC. It has a file database to look up suspicious files and links to free utilities.
This free disk defrag program does a much better job than the windows version. You should defrag your disc once a week.
Stop those nasty pop up ads with this free, but powerful ad blocker. There is also a PRO version of this utility.
Clean your windows registry of invalid entries, unused keys and other references to speed up your PC.