hang and lockup on Shuttle Sk43G system WinXP and Athlon 2000+

I have been running a PVR on a Shuttle SK43G system with WinXP SP2 and
an Athlon 2000+ for a while. It has worked fine all this time. I then
tried to replace the CPU with an Athlon 2600+ and while it booted
okay, after about a few hours, it would lock the system up completely.

Put the old CPU back and alas the lockups are still occurring.
Basically the system with normal Windows services running and my PVR
software (www.gbpvr.com) runs all the time to record shows on demand
but now after a few hours when I go to the machine to use it, it has
frozen and needs to be rebooted.

I have tried the following to fix it

1. Repaired Windows - no dice
2. Run the system in Safe Mode to see if it will stay up - after a few
hours it hangs (when not doing anything)
3. Replaced the 2 512Mb DIMMS with a brand new 1G DIMM - no change
4. Left the machine in the BIOS model with the fan speed monitor.
Stayed up all the time and the temperature of the CPU didn't get above
33C
5. Used the BIOS to set fail safe defaults (so the Athlon 2000+ was
recognized as a Athlon 1250 and the FSB is 266 instead of 333. Seemed
to stay up a bit longer but eventually it locked up.

The only last resort I can think of is to put in a different drive and
a brand new Windows installation. If that fails then I plan to ditch
the machine and get a new one since if it is a MB problem, it's not
really worth repairing

But other options or comments would be appreciated

Thanks

Larry

 

looks pretty thorough...
the only thing I might suggest is downloading speedfan and monitoring
the temperature/voltages while windows is running. after all in bios
mode the cpu is really not doing much and you could still have a heat issue

Also just because these power supplies are notoriously bad...
do you have an ATX ps you could pop in there for a few days?
have you checked the CAPS in the ps or for that matter on the mobo for
bulging?

Oh and how is the air flow around the video card...maybe that is what is
locking up

I know what you mean about upgrading..my sn41g2/pvr is still running
after all these years..I just juiced up the HD to a 500gb ( video is big)
hope this helps