I built a system about 5 years ago for my wife's cousin. She recently indicated that the computer kept shutting off. At first I thought that she had picked up a BIG but that was not the case. I did change the pwr supply,hardrive,disconnected all the peripherals and to no avail.I also added extra artic SILVER to the CPU.I GUESS I need to look at the mobo/processor, but there wasn't any indication of overheating. I monitored the CPU fan and it was operating above 2200 rpms. Any help would be appreciated. I forgot to MENTION the specs.

abit NF-M2S
CRUCIAL 2 GB
ATHLON 3800 DUAL CORE
WINDOWS XP PRO X64DLoad and install SpeedFan....post a screenshot of your temps...both at idle and under load.what is happening now is that even when I boot up it shuts off! I can go into the bios all day long and it dosen't shut off. What happens in safe mode?I have been able to go into safemode but it has shutdown in safemode as well.Then I'm with patio - temperature / psu would be my first thought.