My computer restarts when opening games!

[cabbaca]

I posted a thread a few days ago:
"Hey guys!

I have this really annoying problem! My computer restarts 70% of the time when I open games! When I'm in the game there seems to be no problem what so ever. But the problem have grown to sometimes when I open the internet or receive a skype call... :/ I reinstalled my computer with my Windows 7 disk. When I got in I had a folder called "Windows.old" I deleted that since it had 400GB.
The problem persisted unfortunately and now I have no clue of what to do!

http://img854.imageshack.us/img854/8877/q4ug.png"

Now... things has changed abit and I want to give more info, as the results I have gotten as very wide.
But, at this point, my computer restarts EVERYTIME I open a game! Still there seems to be no problems when I'm in the games. But at this state I can't test that for 100% true, since I can't get in at all. This is atm a huge problem since I'm at some friends house to play! I'm going to the military in less than a month, so a new PC seems abit too much, because I will be away for 9 months.
But the feedback I have received so far, the problems could be my: PSU, CPU, RAM, Graphic Card, Cooler or Motherboard. So at this point I have no clue what so ever of what to do...
I was suggested a Memtest86, but what I seem to find on the net, I'm not 100% sure of what to do exactly, and also I was told it could take more than 24 hours to fully complete.
When I launch games, I have tryed with alot or NO programs/websites open at launch, tho when I got the computer I could have a ton of stuff open when launching!
Please help me, I am clueless!

 

[scout_03]

look like your having a heat issue with the cpu did you try to remove the old paste and repaste with new one system could also need a dust off also your cpu fan run only a 756 rpm max it is a bit low .

 

[cabbaca]

My old CPU fan wasn't working for about 6 months before I noticed it. Could long term overheating result in any further damage of the system? How to increase fan speed at max speed already is not something I know how to. I was dusting off the computer for 2-3 months ago, and when I look inside the computer now, there seems to be very little dust.
The paste I could try out tomorrow if that could be it

 

[scout_03]

then it could have been damage by heat lets see when the repaste done wht happens .

 

[cabbaca]

Okay I got a friend to repaste and I have dusted it off myself. But the problem is still there :/ Any ideas?

 

[scout_03]

what are the temp since you repaste on idle and load also if you could try another psu and gpu separately in the system .