Upgrade most fo PC except mobo, new video card install?

I upgraded most of my PC, except the mobo and CPU essentially.

When I turned on the build for the first time it turned on, beeped, but no video on any input. Someone suggested I remove the card and use the on board video and that worked. I am now installing windows 7.

They also said I would need to change something in my bios. What in my bios do I need to fix to use the new card.

I was using a 4870 before now a 5850, so do I need to remove the old card from the bios or something? Can I just reset the bios since this is nearly a brand new build?