Windows 7 offers plenty of personalization options already, but there are some nice unofficial (and unsigned) themes out there that you can't install without a little tinkering. Normally that requires downloading and patching several Windows .dll files, and it can be kind of a pain in the butt -- especially if you're not the DIY type. Kishan Bagaria has put together Windows Theme Installer for The Windows Club and it makes the process a whole lot easier.