Computer Crash.

[Jeffaa]

I've been playing Civ IV 1.62 for a couple of hours. Suddenly the screen freezes and my screen turns black. I could still hear my music for a short period and hear the game music but after a while i couldn't hear anything.
specs:
3 Ghz
512 mb ram
Ati Radeon 9800 XT

Anything that could be done?

Thanks, Jeffrey