found a thread-dated 22-August 2004 from "BEECHMAN" similar set up and sound problem to me, followed a few replys but dont know whether he got sorted.
ME, I Did an upgrade--Asus A7V8X-X Athlon 2600+ (Barton) graphics and RAM booted up great, no probs !!! but no onboard sound, all is fine in BIOS.(latest) Control Panel> Audio Devices shows AC'97 installed, Device manager>Sound Video and Game, all shows-"working properly" reinstalled drivers several times.
"Googled" this prob. found loads of threads on it but still no answer, as there are a lot of these Asus boards out there, and I've read plenty of threads on this onboard sound thing--- there's got to be an answer.
Any HELP would be very gratefully accepted.