I have below device:
CPU: Intel 3570K
RAM: 8GB DDR3 1600
Mainboard: ASUS P8Z77-V Deluxe (with latest version of BIOS)
Power: Green 685
VGA: AMD 5970
When I changed BIOS of graphic card (AMD 5970) to latest version, my on-board sound card disabled. I don't know how this two components are related to each other?
Please Note: I changed Windows 7 and installed all of drivers again also I refer to warranty service but they didn't help.
Here is screenshot of device manager. All of things are normal: