Computer randomly shuts down

Hi.

I'm having problems with my computer crashing. It will just randomly shut down while playing. Everytime this happened before it would always be in the twillight strand or coast in act1. This wasn't a big problem before, because it basicly only happened in act1, so i didn't lose much time and didn't appear that often (since i got out of the zones fast). But since yesterday it started happening in maps aswell, which is why I post this. I just lost my lvl 86 HC character to a crash in map and I don't feel like playing while I have this problem, since it will most likely just happen again.
I never had this happen in any other game before, therefore im reluctant to think it's a corrupted file or game issue. I tried reinstalling the game but that didn't help.

Any idea what could cause or fix this problem? Problem is that my computer will just shut down, no bluescreen or anything. Just hard reboot. The computer is not overheating or anythnig like that.
I'm not the biggest IT guy, so let me know if i forgot to include anythnig that's necessary to solve the problem.

Thx beforehand :)

Would love to add DxDiag report, But it's too long to add?

EDIT:
Put the DxDiag report in a pastebin:
http://pastebin.com/RD473PWw