unknown problem

Hi,

I've spent almost two months to troubleshoot a problem
that I'd never encountered before. The problem is:

1.Windows 2000 server always halt and will not be alive
more than two days.
2.Can't logoff after logon locally several times.

I've tried the following methods but still can't solve the
problems.

1.Replace all hardwares (CPU (P4 1.8A & 1.5), CPU fan,
Power supply, harddisk (40G Seagate & IBM), IDE cable, DDR
RAM (333 & 266), mainboard (intel D845GEBV2))

2. Reinstall Windows 2000 server with /without drivers,
with /without SP3, with /without enable Terminal services.

Any idea???!!!

KT