Compaq presario random black screen?

I have a compaq presario laptop, and it has a random black screen. This could be in the middle of a game, or browsing the web, or doing nothing. I first thought it was overheating, but it did it multiple times today... What happens is the screen goes black, but is still lit with the back light. All the buttons are lit, and if I press some keys it makes the "incorrect" button press sound or the "ding" . I can never get it out of it except by shutting it off and restarting my laptop. Usually that works for awhile. Today it did it multiple times, within 10min of each other. Does anyone know how to stop my screen from doing this blank thing?