What would keep the headache down to a minimum for you would to do a repair install, which is basically doing an upgrade to the same version, but to do that you need a vista install disk with SP2 already on it.
The only way to get that if you don't have it is from torrent sites, which is dangerous to do as you could end up downloading something wrong and get infected. I could hook you up with a untouched ISO of it but it is a 3GB + file and would take a while to upload it, and I just found out last week that my landlord sold the property and I have to move my business and wife and 5 kids by the end of june. So I am having trouble focusing right now, but trying my best
Normally I would say to let me connect to you remotely with teamviewer so I can look at it myself and see what i can do, but I dont have the time right now and I wont until we are moved as I have to find us a new home!
But if you can get a ISO of vista with SP2 you just have to follow this
http://www.vistax64.com/tutorials/88236-repair-install-vista.htmlOr if you are willing to wait, I can help you at a later date, but note sure you want to wait that long lol
Shane