PC crashes when playing movies(not video games), bunches alrdy tested.

I'm hoping I can get some additional insight into the problem I'm having, as I've reached my wits end on trying to solve this issue.

ISSUE: PC crashes (BSOD) almost exclusively when playing video (movies via VLC, MPC, WMP, itunes, HULU, netflix). Computer runs fine when playing games for hours (ie. Skyrim, CSS, Starcraft 2). The crash to reboot is always accompanied with a loud, single, audio tone... I'm sure you guys know the one. Sometimes it crashes immediately, sometimes 15min in, sometimes an entire movie can be played (2hrs).

the PC has, on very rare occasions, crashed while photoshop was in use and when a game was being played. Also, on rare occasions, the PC doesn't BSOD, it just freezes and reboots.

The computer:
Windows 7 PRO x64
CPU: AMD 9600 Agena
MOBO: Gigabyte MA77O-UD3
GPU: NVIDIA EVGA GTX460
RAM: Corsair 4GBx2 DDR2 800, Crucial 4GBx2 DDR2 667
Primary HD: Seagate Barracuda 250GB, 7200 RPM
Secondary HD: WD 2TB, 7200RPM
PSU: Thermaltake Black Widow TR2-RX 850W
on board audio

TROUBLESHOOTING (already performed): **when I say 'tested' all I'm doing is running a movie via VLC, MPC or WMP (I choose 1 of the 3 at random)

-scanned for viruses via MSS and Malwarebytes' Anti-Malware (clean)
-Reformatted primary HD then reinstalled OS (checked video prior to reinstalling core softwares and PC still crashed)
-removed Corsair RAM and tested (PC still crashed), reinstalled Corsair RAM and removed Crucial RAM and tested (still crashed)
-Ran a stress test on GPU via EVGA's tech support: GPU checked out. Swapped GPU w/ EVGA 8800 GTS and tested: PC crashed
-PSU just replaced a Thermaltake Toughpower 700W: PC has crashed with both PSUs
-Battery Backup was used with both PSUs (I thought there might be an issue with the houses power grid) and still PC still crashes
-stress test was also performed on CPU with Prime95. PC passed no issues, Core Temp confirmed all cores stayed within 34 to 44 degrees celcius.
-Booted the computer in safemode with no issues.... though I didn't test very long (15min) (I don't feel like this was particularly useful since the video can't be properly rendered in safemode: doesn't render full color depth, doesn't display in native resolution etc)....

Yeah... I guess that's everything... seems like the only thing I haven't done is replace the MOBO and CPU. Is there anything I'm overlooking? Anything else you guys could recommend? I'd sure love some help. Thanks in advance