Tell the forum more about your computer. Operating Software, Video (AGP, PCI Card or integrated). Could be many causes for this. Need to know more about the system.
Suggestions: Check in device manager to see if all is well with the hardware. Open the case and check to check if the card is properly seated in slot, if AGP or PCI.
My computer's display is all messed up. I am now getting vertical lines all across the screen. Any thoughts as to why this could be happening?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic