Any help is appericated

The problem.

The pc randomly locks up. When it does the mouse&keyboard stop working and the OS's freezes like a screenshot. This is totally random usage could be 2hours of heavy use or 2minutes of idle desktop. However games (GRAW/Quake4 and Obliv) work fine, even after a lock. Sound and the game will continue but of course no control as kb&mouse locked.

The PC.

It is a pre-built system with no windows install orignally. Nothing is overclocked.

AMD 64bit 3800+ (2.40ghz) Venice Core
ASUS M2V motherboard
1024MB Samsung PC3200
Samsung SATA II 80gig HD
Onboard Real Tek HD soundcard
ASUS Geforce 7600GT Extreme on asus provided 84.21 drivers.
400w PSU
NEC 52x/DVD 16x Rom drive

What I've done.

I installed my own copy of windows Home sp1 then updated to sp2. I then installed my provided drivers with my motherboard, VIA, cool and quiet. May edition. I then installed my old 80gig Western Digital IDE drive. I then started encountering this problem. I took out the HD which was set to single, the orginal system untouched. Formatted and then installed Windows Home sp2 (borrowed) onto the SATA drive. Same issue continues. I've installed with all update drivers on motherboard, via, graphics, sound and Mouse (ms optical 1.1) no change. I've formatted and tried without drivers execpt the sound and mouse, less frequent but still happens. I've tried unplugging the mouse and the keyboard (a different times of course) swapping the mouse, putting the mouse in the USB(this is with and without the keyboard plugged in) No change will lock randomly. All cpu temps are
I also have CPUz, Dx diag and speedfan report avaible.