It's a little risky try this. put in the drivers for the video card and the remove the old drivers for the old video card and then stick in that new card.
Tried to enter the bios and disable the onboard video card but I have no friggin clue what I am even suppose to be looking for once I get into my bios. I see some headings called intergrated something or other but when I hit enter I don't see anything about video cards.
go to control panel
open "system"
go to hardware tab
click on device manager
go to display adapters
look for your old video card - right click and click on disable
restart your computer and you should be using the new video card