Really WEIRD problem!

System
Radeon 9500
Soltek sl75drv5 (KT333) motherboard
OS - Win2k SP3

Reinstalled win2k and installed Radeon Omega 4.4 drivers

Problem - 3d games like UT2003 seem to run fine. Aquamark runs fine. BUT
if I try to run 3DMark 2001 the little splash screen appears - then slowly
pulses into corrupted colours follwed by greying out - this cycles
repeatedly and indefinitely at about 2 second intervals. If I press escape
the 3DMark screen appears normally but if I try to run any of the benchmarks
the system hangs. If I try ctrl-alt-del I get to the task manager initial
screen - if I select task manager it appears but mouse won't work and
keyboard doesn't work properly so I can't stop 3DMark - only way out is a
re-set. I have tried a reformat - reinstall with the same result. This is
weird enough - but the kicker is that if I try using the old hard disk which
still has the previous installation of win2k on it it will run 3DMark with
no problem!!!! This indicates a software problem but I'm damned if I can
work out what it is. Even a minimal install of OS plus graphics card and
drivers gives the same problem and it also occurred when I tried earlier
catalyst drivers. Same problem also occurs with 3DMark 2000!

Unfortunately the old installation has another problem with its network
settings that I can't resolve (try to install any NIC and it fails saying it
can't find a file but doesn't say which file can't be found - googling this
problem suggests that it is pretty well impossible to sort out) so I can't
simply transfer this to the new disk. Basically I'm stumped.

Anyone got any ideas - this one has me baffled!

Tony