Daryl;
I feel your pain. I too have XP & Pro. installed on my system. Due to an unexpected visit by some virus, trojan, or spyware, I decided to reinstall both on my system; whcih I did. Only now I have to choose from the DOS menu which system to boot from, and my entire system is much slower than before (even with both)
In answer to your question; you may have to loose everything else in order to get your OS back working again. I was told the same thing, but since I reinstalled, I found out that most, if not everything, I had on the system before the reinstall, is still there. You just have to dig it out. Thing is, I don't really remember how I got to where these file were located (maybe in program files on the 'c' drive), which is where I began looking for whatever was there. I thought it would be empty. Was I suprised?