Install of new pci sound card

I have a HP Pavilion xe763 pc with a cognac motherboard. I was having trouble with the sound playback from my HD. I installed the pci card but I don’t know how to disable the onboard sound which is supposed to be Crystall AC97. My new card has an install disk, but I can’t find where to delete or disable the onboard. My screen shows Phoenix Bios 4.0 release 6.0.