Um, I can send you something that can recover lost files, even on reformatted drives..
But it sounds like your hard drive might be dying too, that usually explains bad installations and missing files, aside from windows getting buggy from long term usage.

If you cant afford an external or second drive for backups, flash cards and usb readers have gotten pretty cheap, you can probably order a usb connector and 8GB card for like $25 total.

I think its totally viable that my hard drive may be failing as the computer is in no way new (I think I've had it for the past 2 years now going on 3). I have one external drive to back things up on, but somehow, 500GB isn't enough for me as the drive is almost 75% full now (I just re-backed up my (entire) My Documents folder in a DAA file for safe keeping). I also have a number of flash drives... I think 6GB all together (1 4GB, 1 2GB, and 2 512MB) and 1GB of that is full already as well.