Sounds like you have the wrong driver if it's:
a) not playing sound, and
b) not detecting the speaker inputs etc.
I'm intrigued as to what the choice is amongst in the BIOS for you to choose AC'97? as it sounds like W7 might have just chosen a generic driver for the card based upon what's presented to it by the BIOS choice.
I'd:
1) Investigate whether other choices in the BIOS provided a different result
2) Investigate the ASUS website for the correct driver:
ASUSTeK Computer Inc. -Support- Drivers and Download Sabertooth X58 3) Try plugging the speakers into other ports and see whether you get anything
