Aurora R11, green screen then nothing!?

Hi, 

Alienware command center just updated, I started up a game, and then the screen went green and now the pc starts up but won't display anything. The keyboard flashes when first turned on but then stays off. The mouse doesn't seem to get power either. 

I've reseated ram and graphics card, taken out mobo battery and replaced it with a new one and I've tried hooking up to a different monitor. 

It's 3 and a half years old and hasn't given any problems before this.

Any ideas what's wrong with it?

Thanks, 

Rick