do you have the recovery CD that came with it? It will put it back to stock configuration. You can't really fuck it up any more. It's not like there's anything on there that you need. Just reformat it, unless you've already done it. Then just download the drivers and you're good to go.
It's easy. Depending on how old the computer is it might take a while but it's not hard.
"Don't be with someone you can live with, be with someone you can't live without"