Computer randomly turning off

So i got a new gaming PC the other week
Specs here: http://www.ebay.co.uk/...1439.l2649
It has been fine for the past couple of days!

Earlier today, I installed a GTX 670 that i had in my previous computer, the first time I booted it up I downloaded drivers from the Nividia website, and restarted.

I then booted up the PC again and tried to open a folder, then all power went and it would not turn back on, i unplugged the power and left it for 10 minutes, plugged the power back in and it turned back on.
I tried to open the same folder and the same thing happened.

The 3rd time I loaded everything up and began playing Battlefield 4, I played for a good hour and a half on High graphic settings with no problems, I then closed it and changed the theme to my preferred one (Has changing Desktop Background) then started playing Minecraft, the game ran fine for 15 minutes, then my desktop background changed picture and everything turned off again (almost simultaneously)

The power lead is plugged in, and I haven't had any problem with the PC the past couple of days, so I'm wondering if the new GPU has anything to do with it turning off?!

- any help is appreciated

(Sorry for long post:3)

Sounds like an overheating problem with your CPU and or GPU