Hi Jason,
Have you tired booting the PC from a CD or Floppy and running system and disk checks having booted that way?
It might just throw a bit of light on things by taking booting off of a "suspect" the drive out of the equation.
I can burn and post you a boot CD (Knoppix, FreeDos etc.) if you need one.
Regards
Memetic
P.S. If Knoppix sounds a bit alien take a look at this
http://www-106.ibm.com/developerwork...y/l-knopx.html
It's why I carry a Knoppix disk in the laptop drive!