Possible openGL problem with full screen programs

I need to know whether this is a problem with openGL, so i thought this would be the best place to go. Whenever i run full screen games like MoH:AA and Half-Life(Which i had set in openGL mode) My screen always just blanks out when i am just about to enter the first screen, and after openGL has initialised (Just after the command console in games like MoH:AA). The computer never comes out of this, and my monitor looks like my PC has just entered standby, with even the power light changing to standby mode. There are certain things that run, like the demo of The Gladiators, and i think this is beacause they run in only Direct Draw mode. There has to be a solution, seeing as i am almost constantly gaming in my free time i am going kinda mad. Just to let you know, my email address is saxby182@aol.com, and if anyone knows how to help me, i will be glad to supply information to them.