That ASUS board is a socket 478 which is old and long ago discontinued and out of warranty. The MB was released during the XP era. Any Vista drivers available should work, but don't hold your breath regarding there ever been released for the Soundmax chip on your board. ASUS stops updating drivers after the MB is out of warranty and no longer produced. About 3 years.
Put in the MB info here and check for the board's latest drivers.http://support.asus.com/download/download.aspx?model=&SLanguage=en-us
A third party soundcard may be what you need.