Yesterday, after three hours on the phone with Microsoft proving fruitless, I installed XP on the secondary drive that I got last year when the noise first began happening.
Yeah, I probably should've done this ages ago.
Copied over all the user data files. That was the biggest part. Even managed to migrate some of the registry, but things were still iffy. Decided to try repairing the C drive and stepping back to see if I could fix the installation on the secondary ...
After repairing XP on the C drive, and it catastrophically crashing (bad blocks EVERYWHERE), and it being about 3AM, I re-repaired the secondary drive, and all seems well, except I'm having to reinstall about 2/3 of the stuff on the box.
No biggie. However, it did take almost an hour to update with 3 years of security updates. You'd think they'd have that all in one place.
Now the only problem: The secondary disk doesn't have NTLDR on it, and I need it to have the ability to boot standalone so I can remove the flaking disk and give it an honorable burial, as it won't be good for much of anything in a few days. Even now, it's reseeking for no good reason.