Does it only work on NT 4.0?It seems reasonable that it would work on 2K and XP if it worked on NT40. But, whatever, thats your prerogative and I'm not going to try to tell you what to do.
Try loading a different OS, just for the cock of it, and see if it works. Maybe try a different NT install CD, are there any scratches on it?
Also, try installing the OS without any peripherals in it. For example, take out the LAN when installing it. Try a different stick of RAM too. Of course, try all of these things one at a time so maybe you can pinpoint the problem.
I hope this help. Keep posting, keep us updated.