Audio driver for Asus M2N-MX

My brother is having Asus M2N-MX motherboard with him and over there he was able to plug his speakers into the line-out socket and get the sound from it by downloading 64-bit sound driver from the Asus website. But today he has install Windows 7 as his operating system ,as of Windows Vista he try to S/PDIF connected so that he can get sound from it, but he was not able to do so. He has come at my place for help. I have also tried to install drivers by using Compatibility Mode but that do didn't worked for him. Can anyone tell me What can I do to get the sound working again?