We have recommended Microsoft Antispyware
and I found a hidden gem under the covers, a startup manager. Using this screen, you can determine what processes and programs begin executing when you log into your user account. You can find this under the Tools|Advanced Tools|System Explorers menu selection.
This is a great way to clean up those egregious little update programs in the system tray. Quicktime, Logitech, Java updater, you name it. You’ll also find that your machine will usually start more quickly, and that you’ll have a little more memory for running the programs that you want to run.
For more on the topic, see the book Degunking Windows by Jeff Dunteman and Jolli Ballew.