Video not working

[monkeystew580]

Whenever I tried to play Portal 2 on my computer today, it wouldn't work. I first tried Coop and after the game started, all I could see was black, the subtitles, and the crosshair. The same thing happened to me in campaign. The game worked on all of my other computers but not on this one. Has this happened to anyone else? If so, please tell me how to fix it. Thanks.

[Berti]

Are you sure your PC meets the minimum requirements to run Portal 2? Also, are your video drivers up-to-date?

[monkeystew580]

Checked that. Yes and yes.