Read this thread as it should get you started in getting your ISA sound card working in Slackware, which is more of a daunting task in Slackware compared to Mandrake, as it lacks the detection and configuration tools that Mandrake has.
http://www.linuxquestions.org/questi...p+soundblaster
But following these simple instructions should get you going in no time with sound. Ask away if you get lost or confused.