How do I install my video card?

I just got a new computer that already has an nVidia graphics card in it, but I have a better one. I tried to install it, but everytime I click on install driver, the installer just closes and both video cards are not working. How can I disable the default one and use the one I bought?|||go into the bios settings <usually a delete key during the post process right after you power up> from the bios settings disable the onboard video card