Hardware problem

[givos]

Hey.
I need your help. First i want to say sorry for my bad english .
I have:
-i7 2600k
-croshair 16gb ddr3 ram
-motherboard asus p8z68-v
-700w

Problem:
I bought 3item(ram,cpu,motherboard) in September. It was working fine till past week. When I am on Firefox or watching movies , etc my computer shoutdown.. I dont have any cloue why. In bios sais cpu have 69c ??? Atm i am testing ram with memtest (i am writing on diffrent computer ), so far no errors
But interesting is if my computer dont shoutdown and restart i go in battlefield 3 and i can play for about 1hour(it restarts if i go on desktop) I already format.
I usualy talk on skype when i am playing. When it restarts or it seems it is restarting i can still talk with other players.
And 1 more thing. When it restarts, fan goes on max(i think cpu fan).


I hope anyone understand me and know what is wrong.
Thank you

 

[davcon]

What psu make and model and gpu?

 

[givos]

name power(lc8700), 700w
gpu radeon 6950 hd