http://theopen.org/files/whatnot/WinNuke.zip
This little "utility" belies it's name as it does not nuke Windows, and although I have not used it myself (can not be bothered to franky ) the author claims it backs up what it takes in the windows temp directory and is completely reversible. In fact, everything will work just like it always has done, but one factor has "changed".
If anyone is stupid enough to use this, or just wants to give the rest of us a big laugh. Be our guest (B&TB style) .