Asus P5GD2 Deluxe. I've disabled all the "wake on" events I can find, and still the PC restarts after being shutdown from WindowsXP. Sometimes 5 sec. later, sometimes 10 min. later. Also set all BIOS options to default. What the hell is this? Thanks...

Could be that you have the a virus , for example fake antivirus spysheriff infecting your PC, that causes Windows to shutdown randomly.

Your PC could be overheating. Check that your fans are free of dust, that includes CPU, PSU and also any fans on motherboard devices.

Your PSU could be under par for the task. I didn't take the time to check your signature, sorry. If a PSU is being tested muchos then it might get hot and have a little lie down.

Er...driver instabilities?

Perhaps it's just because Microsoft are poo.

Disconnect 'phone lead (if present) and network cable. Check in BIOS is set to 'Power Off' not 'Standby' on pressing Power Button. Swap Power and Reset button connectors on motherboard to see if dodgy Power Button.

Mike.

could be a "wake-on"setting e.g. LAN
Sometimes a failing PSU will also cause this.

Thx for the suggestions. The problem was actually from within Windows: the integrated ethernet controller driver has properties accessible from Device Manager. I disabled the wake capabitly there & all is good now...