Ok what you need to do:
1. Uninstall all graphic card drivers. This includes the onboard as well as the nvidia.
2. In bios disable the onboard card.
3. Rerun the nvidia driver installation.
4. Reboot.
You can't run the on board with the nvidia at the same time. If that doesn't work you'll need to tell us your specs like the video card you bought the mother board you have and wether it has an integrated graphics card.