ASUS A7M266-D 2 ATHLON 2.2GHz 1GB RAM 120MB HARD DRIVE WIN XP PRO SP1 ALBATRON GFORCE4 BUILT IN SOUND RAN STABLE FOR 3 MONTHS Recently while rendering video (Adobe Premier) my system began to shut itself off after about 10 minutes of processing. I have also noted that it does the same at times during some game play. When this happens, each time I reboot the OS makes it to the login screen, after a couple of seconds locks for about 5 to 10 seconds, then shuts off again. Sometimes it doesn't make it to the login screen but just shuts off. Does the same in safe mode. Sometimes booting with previously known good settings works for a while, but not always. RAM has been swapped out. Recent Changes: DirectX 9.0 installed, Adobe After Effects installed (but run successfully for a few days before problem started). Usually takes 5 to 15 reboots for the system to come back up "normally", but still unpredictable. Windows rarely detects any previous problem with booting during the next boot. Never checks disks. Doesn't detect previous reset unless it happens before the login screen, then says that windows failed to start properly last time.

I have the same problem with my System. I have recently updated the bios to the most recent one available and so far so good,(but its only been a day) but as you say it is unpredictable. It can go a week or more with no problem and then do it repeatedly for a day or two before becoming stable again. In summary, you could try updating bios

Check whether or not your power supplies are adequate and if you have adequate cooling for your processor and case.

may be your motherboard detects the high temp from cpu and shuts the system off. check the bios setting. Any hardware change lately? such as adding a new hd, some 10k scsi hd generate a lot of heat and if your mb detects too hot, it just shut itself off.

Temp appears to be OK. Doesn't get above 46C on chips and 35C on Motherboard. Limits is around 69C.