BSOD playing various games, unknown (and seemingly different) reasons

Hi there,
my computer crashes from time to time. As far as I've noticed it only happens when I play games. It isn't any game in particular, but as far as I remember it has happened in the following:
Skyrim
Just Cause 2
Saints Row: The Third
Terraria
Call of Duty: Modern Warfare 3

I've only recently enabled minidumps, so I have at the moment only one minidump to attach. I will upload more when my computer crashes again.

Some additional info:
Sometimes the computer crashes without any BSOD.
The screen often looks strange before the crash. A lot of small lines in different colors, everywhere on the screen. Like if the pixels were 50 px wide.
I have two monitors plugged in and one TV (through HDMI). I don't know if that changes anything, but anyway it can be worth mentioning.
I've run Memtest86+ for seven passes, no errors found.

Attached is the Seven Forums zip, containing info and the minidump.

Thanks in advance!