Chkdsk /r 70% complete for about 20 hours now

Try running repair on windows...or if you can, boot into safe mode, start/run sfc /scannow if neither of those work....Sounds like a bad harddrive....slave it into another machine, get what you can off of it and kiss it goodbye.

Try a registry restore, there are instructions on the MS support website. Basically, it involves lots of command lines to restore the registry to the default settings and then using a system restore point registry to get back to the original config.