Unexplainable bug

Tanitha: Ive owned computer shops for a long time. "Usually" these blue screens are from either virus's, or overheating. There's lots of other uncommon reasons. But they are the main two.
And id say overheating is your most probable cause.
There's a big CPU fan, and a decent sized fan on your graphics card/chip, and sometimes a smaller fan on another mother board chip, and a fan in your power supply.
The big CPU Fan and the fan on the graphics card both suck a lot of air into them, this also sucks dust in. They clog and either slow down or stop pretty easily. I usually have to pull mine apart every 3-6 months and vacuum them out.
When your computer works hard, "like playing a 3D graphical game" The CPU and graphics card get hotter, if your fans cant cope the chips temperature will get too hot, and they will blue screen your computer and switch off.
A graphical 3D game will work you CPU and graphics card, a lot more than most other things will. So it overheats while playing WoT, but doesn't overheat otherwise.
I suggest you take a look at those fans for starters.
And I hope that helps.
If your fan's are ok, and you have run a decent virus scanner (like Avast which is free), you could always uninstall then reinstall the game.