Opti did not make sound cards, just the chipsets. As they sold this business, they no longer offer reference drivers, but they do provide the following links to manufacturers who used their chipsets: http://www.opti-inc.com/my_html/part_mm.html I realize many of the links are dead, but you are talking about a pretty old sound card.

Don't know if its any help, but I've got a driver disk w/ 95 and 3.1 drivers for a card based on the 82c931 chip. These date to about 1996. I'm surprised 98 doesn't detect the card