Kitty

I've just started using a new PC with vista, but for some reason the monitor turns itself off like it's in sleep mode(which I have disabled via control panel), I press the power button on the monitor and it turns on for a second(the power LED, not the screen), but then shuts off again so I have to turn the PC off at the power button and restart windows. It does it more frequently when It's running games. Anyone have any ideas what I can do? because I'm stuck.