Could be a change in driver or connected to another port. Some PCs have onboard video and you wanted to use the other card. Tell more about this PC.
So I just transferred my PC to a new case and now for some reason my screen stretches vertically. When I go into screen settings it says 1920x1080 which is the resolution of the display, but now it's like it's stretching over two displays that are vertical. Another way to describe it would be that it's like it's rendering windows at the correct resolution but it's stretching the image vertically so only the top half of windows is showing on my screen. Any ideas on what would cause this?
Cheers

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic