Maziar has a point ,sometimes ATI cards will not work if nvidia drivers are installed .
My video card is toast. All it shows is a bunch of scribbly lines, I can't ready anything. How do I remove the old drivers of the bad video card if I can't see anything? I'm upgrading from an Nvidia GS 7100 to an ATI Radeon 5670. When I put the new video card in, all it shows is a black screen, the monitor is not getting a signal. I have a 650 watt PSU.
eqbal321a is right. I had the same problem installing an NVidia card with an integrated ATI video controller.