Run programs like AdAware, SpyBot, Spyware blaster, and Spyguard. The first three programs will clean out any spyware progams installed on your computer. The last one will help keep your computer from being infected with spyware.

Once you remove the spyware, you should see a noticable difference in performance. At that point you should begin using the Ad/Remove program tool in control panel to remove any unwanted programs.

Once your unwanted programs have been removed and you have cleared up disk space, it would be a good time to defrag your system.