Computer occasionally restarts itself on left-click

[Harry_Beast]

I recently reformatted hard drive-reloaded WINXPhome and all appropriate drivers-system okay--Then I installed 3dmark5 and rivatuner
I bumped up core to 500 from 300 --what I was using before format.
That was 2days ago--now computer has rebooted itself 3 times today--always when I left click on something---the last time I was just deleting mail!!
Also screen froze when I ran 3dmark5---which it did before format-(reason I did Format)But-I used to be able to run the benchmark to completion with no problem.
The mobo is AsusP4s8x card GF6600gt
Any advice will be appreciated!!

 

[Harry_Beast]

Problem solved

I turned off the auto-start on critical error and got the Blue Screen of Death
That error message indicated a hardware problem.
I had recently reformatted my hard drive and downloaded the current drivers for my vid card---So now I used the disc that came with the card and loaded the drivers from there--problem solved!
I also had a floating error message :sync not in range!-downloaded the proper driver my my monitor--problem solved!
So--if you learn by your mistakes--I am getting a real edjamacation!!(lol)