ASUS does not list sound drivers for Vista. Thus your friend is limited to the Windows "HD Audio Codec", if it is even compatible. If not, he will have to install a separate sound card that is Vista/Win 7 compatible.
Looking at the drivers for that motherboard, it was designed for older OS', including Windows 2000, etc. Even XP drivers will not work since some sound functions are handled differently than the older OS'. More and more a separate sound card sounds like the best solution. There are inexpensive $20 to $30 range sound cards that will perform as good or even better than the on-board audio.