Diagnosing System Freeze

[superfuzzy]

A family member is using a 2.1GHz Intel Celeron based system that I build about 3 years ago. It's only used for surfing the web and Word, so is adequate.

After being powered up in XP for an hour or so the screen goes blank and the system is unresponsive.

What I've done:
-When it is booted with a Linux Live CD it stays on, and working, so I think it must be an OS (XP) problem.
-The System Log under Administrative Tools has no errors
-Under "Power Options" everything is left on

Any suggestions for what else I can try?

 

[superfuzzy]

Not one single suggestion

 

[josephmil]

Re-install the OS.

If that doesn't work then check the temps for the CPU and HDD.

If that doesn't work then I don't know.