Disabling motherboard sound cards

I am helping a friend with his obsolete Ultinet system and am ready to learn how to disconnect/turn off a motherboard sound card in order to install a new one. Details: 686 AMIBIOS 995 American Megatrends BC25262, ESS Audio Driver ESI869F G240 TTUC6696A, Pentium II, MS Win95, what else? (I know, save your keystrokes about the ancient equipment. This is as much for my education as it is for my friend’s equipment. See further my post in the College Degree/On the job experience discussion