Diseased and Suffering Binary Buddy

My cherished companion has virus damage; the offenders have been purged, but the damage is real. Most of my Windows System programs have been seriously crippled. I can access them in Safe Mode and by circuitous routes, but it's a hassle. My old friend is very slow and is getting slower every day. Some background: my buddy originally had Me installed, and when it failed, I had to overwrite the OS. My friend had an XP Pro disc, so I installed XP Pro over the Me. Everything went well for a while, then the damage was wrought by hideous human beings (if I may so call them) through their evil and nefarious projects. Anyhow, now Microsoft will not support this OS, and it does no good to reinstall the OS. Compaq will not support this OS because it is HP's policy to not support any other OS than what originally came with the computer. That's where I am. I need an independent agent who has the ability to scan and hopefully repair -- or, at least, name the files and drivers that were damaged. I have been unsuccessful in finding the right search words to find an agent who can do what I need to be done. I do not have the money to have a technician visit my ill "baby." I don't believe in computhenasia, but the life is draining from a very useful family member. I would appreciate any nudge in the right direction from y'ns who are gifted in this area.