What causes laptop black screen then freeze?

Hey all so my friend owns a laptop and has recently been having issues where the screen goes black the computer will freeze and have to be manually rebooted. He is in a different province atm so can't really go over to his house to check it out myself.

When it happens he says he can be on msn and have firefox open and it will happen. It also happens during sc2 and sometimes he said the computer was idle and it happened.

So far I told him to check temps for his gpu forgot what it was think it was a radeon 5xxx and the cpu was an i3 forgot specifically which one. He said when he was playing sc2 temps went as high as 83. I was thinking maybe the graphics card was overheating or but he said it happens when doing things that aren't graphic intensive

So any suggestions on things he can try?