Compare the age of Redhat 9 and it's packages to the age of the mobo/sound device, if Redhat is older (and it is fairly old) i doubt it is going to auto detect the hardware.
You will need to setup ALSA (redhat might even use old OSS drivers?) and load the correct modules for your sound card. I used the arch linux wiki, but had a quick look and i think it'd be quite difficult to adapt to Redhat (using Udev etc.).
Is there a particular reason for RH9? Newer distros will do a much better job of autodetection, such as Fedora core if you want to stick with redhat.
Sorry i couldnt be more help.