I'm not on RH right now (am at work), so I couldn't tell you exactly - but the System Settings would be my best bet.
And since you're playing games when it happens, it sounds like a driver problem (or memory problem) of some sort. You might try installing new drivers for your vid card or cleaning the contacts on your RAM (w/an eraser).
How happy is the blameless Vestal's lot!
The world forgetting, by the world forgot
Eternal sunshine of the spotless mind!
Each pray'r accepted, and each wish resign'd.