Program or hardware problem?

Having a weird problem when the computer sits idle or quiting out of games the computer restarts itself. This only started happening a few days ago. However I got home tonight after taking my kids for a ride and the Computer was frozen on the ASUS welcome page (the one were you can press delete or tab for system info) It took a lot of restarts and disconnecting the second hard drive to get it going again. I have run AVG, Asquared, spybot , Adaware and Spyblaster with no results, a clean system. I have checked the event log, nothing there. The only thing that is not working properly is PerfectDisk 8.0. By not working I mean that the offline defrag is not working and in the event log this is the last program to start?

I am thinking I have a problem with PerfectDisk or a power supply problem. Is there any way to check the power supply through a program as I do not have a multimeter or a spare power box. Once I have the system running there is no problem, only if I leave it idle.

System specs
xp sp 1
6400 2.13GHz
2GB Ram
Geforce 7600 GT
Asus P5LD2 Se


Any ideas would be greatly appreciated.



System specs
xp sp 1
6400 2.13GHz
2GB Ram
Geforce 7600 GT
Asus P5LD2 Se

 

My computer>properties>advanced>startup and recovery>uncheck automaticaly restart.And why you don't have SP2?Try to install SP2 cos some apps will run smoothly if you have SP2 and the updates.

 

I have tried to install it.My CP just stays idle, I have let the process run for 12hrs with no result.

 

Okay did this. And I can reboot with no problems. However My Pc is still restarting for no reason that I can find. In event viewer I am getting this message :

The user restarted or shut down the computer by clicking Start or pressing CTRL+ALT+DELETE, and then clicking Shut Down. The message displays the Windows product information for the computer logging the message, including the product name, version, build number, service pack number, and operating system type.

This corresponds with the time the system restarted. I am not doing this?

 

do you install sp2?
do you uncheck automaticaly restart?