I'm not even going to bother at this point. I just experienced the problem while running Sam & Max at 640x480 on the CRT. Two nearly completely different systems experiencing the exact same problem. Drivers and video card are among the things wholly different.
What I'd guess at this point is the hard drive has gone bad. Maybe it's wrong, but it's the only common element between the two builds that could possibly do this, unless a mouse, keyboard, and headset have more impact than I ever imagined. If the hard drive goes bad, it could cause the system to behave in this fashion, n'es?
Anyway, I'll have my uncle deal with it (he's my system builder). He'll be able to test for that faster and easier than I will. Though, with the amount of problems I have ever time I hire him to build a computer, I imagine he might turn me down next time. hahaha