Random restarts/BSOD when GPU under load

Hi there,

Hopefully followed all the guidelines to provide enough information so here goes... I've been getting some random restarts on my PC, one last year and then two on subsequent days back to back just now. It seems to happen when the GPU is under stress, such as when playing a game or after playing one. I've also noticed some microstuttering while listening to music or watching a video.

Things I have already checked:

1. Memory. Ran the Windows Memory Diagnostic, no problems detected.

2. ATI drivers are up to date on the graphics card.

3. Temperatures on the CPU and GPU appear to be fine; GPU peaks at around 50c while playing a game, CPU averages around 35c at rest.

4. I know there is a random unidentified hardware device on the PC but I have no idea what this is: When I've tried to find software for it Windows doesn't recognize it and can't find anything.

5. It may or may not be related, but the PC has problems starting up from cold (power off at the wall); fuzzy green lines will display on the loading Windows screen and the hard disk info screen and Windows will fail to load. Restarting the PC solves the issue and it boots normally.

Any advice you can provide would be most welcome.

Apologies, I know it's not good etiquette to bump one's own thread, but I have some more info to add.

I've solved an issue with the secondary backup drive being marked as the System drive even though it wasn't; it hasn't randomly restarted again yet while in use but it did boot with green fuzzy lines, then restarts by itself and is fine on the subsequent boot (no green lines). I can also confirm the inside of the computer is pretty clean; I've regularly checked for dust build up to prevent overheating.

Hope this extra stuff may be useful if anyone can provide advice. :)

No one at all? That's a shame.

It's now randomly restarted when not doing anything; it was sitting at the locked screen with Firefox open in the background. From looking around I've tried disabling hardware acceleration in Flash and Firefox but I'm wondering if a transistor is blown or something. I know the issue is the display adapter because Windows says the problem was caused by it, but whenever it tries to open the "solution" it says it can't connect to the Internet (which is wrong it's working fine).