Diamond made a large variety of soundcards using various chipsets. You need to know exactly which card you have, then go to.

http://www.driverguide.com/

login name = drivers

password = all

Use the advanced search, follow the drop-down menus and you'll find dozens of drivers!!

It might be easiest to remove the card & note down everything printed on it and the principal i.c's.

Good Luck

John