It has always been a problem for me that I go through certain phases of rapidly installing and uninstalling software when looking for a good utility.
Typically that means lots and lots of registry entries that never get cleaned out and eventually my PC grinds to a halt, forcing me to spend 2 days on reformatting and reinstalling.
I read about SVS on Lifehacker today and it seems like an extremely useful solution.
A free virtualization program that traps all changes made by a program in a separate layer, allowing you to keep your base OS clean. Uninstalling is as simple as deactivating a “layer” and voila! all files and registry settings disappear.
You can read more about SVS in this lifehacker article.