Need help identifying computer problem. Computer keeps crashing when playing games

[Gadge89]

Hey I've got a problem with my computer and i cant figure out what it is exactly so i dont know where to start on fixing this.
Basicly when im playing a high powered game i.e World of Warcraft its crashing quite often turning the window into a black screen and then crashing my computer, as if its something to do with my graphics or spec not able to run it.
I cracked my computer screen a few months ago and lately got it fixed and since then this problem started to apear, i've never had a problem with this before then, I thought it may possibly be from getting a new screen i might need to reinstall my graphics drivers which i moved onto doing and it still didnt help my problem


I've got 3.00 GB of RAM
Processor: Intel(R) Core(TM)2 Duo CPU T9400 @ 2.53GHz
My 2 graphics cards are ATI Mobility Radeon HD 3870

So its more then enough for world of warcraft or most other high spec games
It would be greatly Appriciated for your help.

 

[gbhall]

Usual cause of this problem is overheating and/or weak power supply.

 

[almcneil]

Your computer may not be crashing, rather, your monitor is cutting out because it's not fixed properly. Can your borrow another monitor and swap it and see if the problem still happens?

-- Andy

 

[Gadge89]

its an alienware laptop that im using, i took it back to the shop and he said he spent a few nights on it stripping it down and putting it back together then said he uninstalled WoW and reinstalled it and it seemed to be running okay, but it wasn't i got it home and it did the same thing, besides surely a game cant crash out your full computer? shouldn't that be something to do on the hardware side?