For about a week now, when I try to play a game on my PC (HP Pavilion a6813w), after ten minutes or so my monitor will go to sleep. I have to cut the power and restart the system before my monitor shows anything again (Keyboard/mouse) does not wake the computer) . I installed an Nvidia GeForce 9400 graphics card six months ago and everything worked fine until last week. I called HP support for help and she eventually told me I need to do a system restore. Does anyone have any idea?

this could be a different problem but i know a few people with hp computers that had a similar problem and it turned out to be the video card over heating

If that is the case, what do I do to stop it?