Try this: Press Ctrl-Alt-Del (and then click Task Manager, if you're running Vista), then click the Processes tab. Ever wonder what all those items are? You should, especially if you're trying to troubleshoot a slow or malware-infested system. The list represents every single process that's currently running-good, bad, and potentially dangerous.
Of course, unless you're a computer-science major (with a 4.0 GPA), you'll be hard-processed to figure out just what all those processes actually are. Enter ProcessScanner, a free utility that scans your PC and gives you a detailed report about each process: how much memory it's using, whether it's a security threat, and so on.
The program pairs with the ProcessLibrary.com site (where you can type the name of any individual process and get an instant description), tapping the latter's database to present detailed scan results in a browser window.
Upon reviewing the report, you may find apps you want to uninstall to improve performance or even malware that needs to be eradicated. This is definitely a worthwhile tool for any diligent Windows user. I just made it a permanent addition to my utilities arsenal.