TweakNow WinSecret Professional

There are plenty of Windows tweakers out there. However, what's nice about WinSecret Professional is the fact that it groups things into easy to read categories and allows you to customize your system but with the easy to use interface. Point and click.

Nice. And there are many features within each category, so it's probably well worth your time to take a look at all of them the first time around to make sure you've definitely got your system running the way you want it to run. Freeware for Windows XP and Vista, both 32bit and 64bit.