I don't think I had to do anything special when I went from an onboard NVIDIA Geforce7050PV/nForce 630a to a Radeon X1650. I think I left the original nForce driver alone, downloaded the ATI drivers, ...
I have a ECS Elitegroup P4 Mainboard P4VMM2, and it has a S3 graphics prosavage 32mb card integrated, it's okay, but i want to upgrade to a Radeon 9600 or a GeForce Fx 5600, I have the 4xAGP slot ...