Cheat Engine

[SF]

Just use the Restore to Factory Default option, it's the easiest.

You could also insert the OS disc and do a format, but you would have to go driver hunting after that, easier to just restore to factory default.

[Hero]

if its store bought, most pcs have an option on the first screen when it boots. Other wise you need an install disc.

[Hero]

It does exactly what it says. Returns it to the factory settings and standards. Basicly as if you just took it out of the box.