PC will shut down while watching any video on both IE7 and Firefox

::Hello ppl::

::I'm having problems with my rig, My PC will shut down when I watc
any online video like in youtube or any other site for that matter.
tested RAM using the memory tester that comes with the OS and i
indicated no issues, I then updated my video card drivers, still hav
the issue, downloaded the omega drivers which I've used before to solv
video card driver issues, still have the issue, updated then my BIOS t
its latest version, I still have the issue. So I decided to format th
machine and reinstall OS again and after reinstalling OS I installed al
updates from Win Update, and tested... still same issue, I then us
Driver Genius Pro 2008, update the app, used it to scan my drivers
downloaded all drivers that need to be updated (none which were video)
installed them, tested... same issue. I can do anything else without th
machine shutting down. Asides for what I've done is there anything els
to do??? Below a synopsis with system specs. Many thanx in advance
.:

::Problem: PC shuts down while watching any video on any website usin
both IE7 and Firefox.:
::It will run DVD movies, play Video games and play movies stored i
the hard drive without shutting down.:

::Steps taken already: tested RAM, BIOS update, driver update, flas
player update, reformatting PC, installing all updates first, the
installing flash player.:

::Waiting for: friend with another Video card (8800GT) to discard o
prove bad Video Card theory:

::System Specs::

::OS: Windows Vista Ultimate X64 SP1 (last update was today march
2009):
::CPU: Intel Core i7 920 :
::Motherboard: Asus P6T Deluxe :
::Memory: OCZ Gold Edition Tri Channel 12GB PC10666 DDR3 Memory
1333MHz, 12288MB (6 x 2048MB) :
::Graphics Card: Nvidia Gforce 8500GT :
::Sound Card: Motherboard's stock Sound Card :
::Monitor Display: Compaq WF1907 :
::Screen Resolution: 1400x900 :
::Hard Drives: Western Digital 500 GB :
::PSU: Ultra X3 1000W :
::Case: Thermaltake Kandalf LCS Black :
::Cooling: CPU Stock fan (no one ships nor carries the bracket for cor
i7 waterblock here in Puerto Rico yet):

--
BongVader