Computer Crashes When Starting Up Games

Hi, over the last few weeks, infact months my computer has been randomly crashing at first we thought it was the memory and then we thought it was to do with the power, both problems we tried to resolve but to no success. My graphics card is the ATI Radeon HD 5870, I have the most recent driver as I installed it just last week, every time I try playing a game, although not a browser game my computer crashes within the first 20 seconds, wheither or not it's still at the menu screen of the game. If anyone could help me with this problem I would greatly appreciate it.

Alex

 

Is it the game itself crashing, or the whole CPU? If you load custom files into games it can cause the game to crash. That's what I had happen to me with Fallout New Vegas. If it is the computer itself let me know, I can probably help you.

 

Define crash..

Like blue screen?
Just a reboot?
Does you still hear the fans and the screen is just black?
Check your windows logs too and try to see what happened right before the crash.