Turn Windows XP Into a Fake Windows 7

From Gizmodo -

If you want the look of Windows 7 but don't want to use a beta OS, you can do so with Niwradsoft Seven Remix XP. It is a free download that transforms the entire look of your OS to be all-around 7-like. You get boot screens, logon screens, screensaver, system theme, and loads of hacked resource files.

Download page here.