my winxp keeps on freezing, all hardware seems to be working

[LOUISSSSS]

i've checked all my hardware parts and they all seem to work fine:

hardware tests done:
CPU: OCCT 2hours PASS, Linpack (50 passes) PASS, P95 12hours PASS
RAM: Memtest86+ 24hours PASS
Harddrive: hdtune: benchmark+scan PASS
Video Card: ATI Tool Scan 10 minutes PASS
psu: just replaced w/ PCPC silencer 610. (problem existed w/ old psu also)

the problem is that my windows would hang after a random time period, it seems to be at least a few hours after booting up. It rarely freezes within an hour of booting up.
Both of my screens freeze, mouse freezes, clock, sidebar cpu/ram/network/disk meter freezes and does not resume until i restart pc). i dont get a BSOD or anything.

let me know what else i can do to help diagnose the problem on my system

 

[LOUISSSSS]

bump

 

[theAnimal]

Try Furmark for the video card, and more than 10 minutes.

 

[LOUISSSSS]

done, worked 100% with temps under 80c at load...

Load line calibration is off by the way, (does this matter)? i've even had voltages up to 1.4vCore for a Q6600 @ 3.2ghz just to see if it was a voltage problem