Startup loop after in-place upgrade

I recently ran an online diagnostic on my Win2k box.
{{Huge mistake by the way; keep away from pcpitstop.com}}
The box was functional, but there was a couple glitches
that wasn't there before the scans took place. After a
couple frustrating days of trying to repair it, I just did
an in-place upgrade. Now, I cannot even boot into Windows.
I cannot even get to the 'Starting Windows' bar graph. It
loops at the IRQ window, therefore, I cannot get to the F8
option to get into safe mode.

I have been to other message boards that show similar
problems, but they always point to some hardware
incompatiability. The system was running prior to the
in-place upgrade, so I seriously doubt it could be that.
It has to be a missing or corrupted file that is preventing
me from going any further, but what...?? I would
appreciate any help on this problem. Thank you.