Hello, I built a computer with an ASROCK N7AD motherboard, intel dual processor, and an ati xt 1900 video card. and when i installed the drivers for the card my screen gets broken up lines going horizontally across it and after a few moments my computer just blue screens.
More aboutgraphics nvidia chipset
There should be no problem putting an ATI card on a Nvidia chipset. Did you uninstall the Nvidia graphics drivers first? If not that can cause issues.
As jyjjy said, ATI cards will work fine on nvidia chipsets, you just wont be able to crossfire, only sli.. and by the sounds of it probably driver issues as said, try booting in safe mode and make sure all old drivers are no longer there