RegToy

The number of settings you can change is astonishing. Vista users will particularly welcome it, because it gives you control over many Vista-specific features. In Vista, you can turn the Windows Mobility Center on and off, disable Windows error reporting, hiding the Control Panel, and much more.

Note that if you install this for Windows Vista, you'll have to install it as an administrator. And if you install it for XP, you'll have to download Microsoft .NET Framework 2.0.

--Preston Gralla