Because the 6850 card has an audio chip on it, the integrated audio chip on the motherboard has been automatically disabled.
You can re-enable it in BIOS Setup, then you should be good to go.
The Driver Scan software could not detect the integrated sound chip (because it's disabled as I explained above) and that's why it said you needed the AMD HD driver (because that's the only sound chip it can currently detect).
You don't need the AMD HD sound driver unless you want to use the card's audio capabilities via it's HDMI port or it's DisplayPort, instead of the sound chip that's on the motherboard.