Full Screen Videos cause computer to crash

So I've had this computer since September and have not been having any issues until I updated to Windows 7 from Vista. Everything works fine and dandy until I decide to watch a video in full screen mode. It is the worst when watching online videos. Once the computer crashes the screen goes blank and all sound cuts out. The only way to restore the computer is to force it off. For online videos this happens in a few minutes or sometimes a few seconds and for downloaded videos this happens after a little longer, usually around thirty minutes. I have uninstalled and reinstalled all of the graphics and sound drivers and have run hard ware diagnostics on everything repeatedly. Any ideas? Also I do play very taxing games on this computer but I have never had any such issue.

In search progs/files
type dxdiag
and tell us if direct x features are all working (ie "Enabled") on the 'display' report page plus look at both the sound pages in the white box should say no problems found

Hey, I have the same problem here, ive tried setting it back to factory settings thus reinstalling windows. All the directx features are working with no reported problem there.
I don't think it's a memory issue in the computer, as my specs are:
Windows 7 64-bit
Processor: intel core i5 3.20 GHz
Ram: 8 GB
Graphics card: NVIDIA GeForce GT 220
Graphics card memory: 0.5 GB
Any other ideas? When it crashes the screen turns black while the speakers give out a buzzing noise. Everything is unresposive the only solution is to turn it off with the power button. It happens in any full screen video online or offline and even visualizations from windows media player and iTunes, but only in full screen. I don't think it's overheating either because sometimes it takes 30 mins to crash and other times it will crash immediately when put in full screen.