So, despite the 24 hour (or was it 48, forgot that detail) burn-in test done, the system is not stable.

the problem being that I can't afford to test it right now; if it fails then I've got a week's worth of installing and setting up to do.
-nudone
You just have to set up that machine right. And it might involve a full re-install of Windows.
I know you said you updated all and every driver in the system, but that doesn't mean Windows isn't corrupted in some way. I've seen that happen from
Windows 3.11 MS-DOS 2.x to Windows 7, and all versions in between. Just starting over with a format c: /s and restarting the tedious job of re-installing Windows and all your required software will eventually fix the issue. I understand you are not (yet) ready to go there.
About 15 % chance the memory (probably just 1 module) in the system is the cause of trouble (even after a burn-in test!)
About 10 % chance the video adapter/drivers is the cause of the trouble
About 5 % chance the hard-drive (boot/swap) is the cause of the trouble
About 0.01 % chance the
PS/2 keyboard is the cause of trouble (saw that about twice in about 2000+ PC's in all my years building of PC's)
The rest (~70 %!) is caused by Windows not installed/decompressed right.
(Percentages are estimates)
Just my
