Question on replacing other card drivers

[Waldo]

I've built this system and used two different nvidia cards, and had to remove the previous drivers when installing the second card. Now I'm installing an ATI Radeon 5870 card. Will the nvidia drivers be ignored or do I need to remove them ?

 

[dividebyzero]

You will need to remove them.
Uninstall using the nVidia uninstaller then use Driver Sweeper to remove any remnants of the nVidia driver and PhysX components would be your best bet.