I had the same problem. Go to:
http://www.tldp.org/HOWTO/K7s5a-HOWTO.html
Title: The Elite's K7s5a mainboard HOWTO
Subtitle: How to use Elite's K7s5a mainboard under GNU/Linux.
click on the link "2.3 Kernel Approach: The AC'97 Driver"
I typed "modprobe i810_audio" --> now mp3s and audio CD work fine. Note: I did not get terminal output like the article says. No biggie, but weird. I have not rebooted yet, so I may still need to issue the "echo..." command like the article says. If that doesn't work, I'll try to remember to post here again.