Hi i installed Slackware 8.1 on my Pentium MMX 233 MHz box
81 MB Ram Diamond Stealth II S220 Video Card and a Creative Sound Blaster 16 Sound Card
installing worked perfect ( had to select few as posibel packages because the installing hd is only 1.2 gb but i have an other hd 1 gb
wel i configured the X system had to use vesa as the drive nothing else would work not even the drivers in the driver list
after that i started booting into KDE looked beautifel ^^ then i got this error
device /dev/dsp can't be opened (No such device)

lsmod returned me:
Module Size Used By
soundcore 3236 0
pcmcia_core 40896 0
ide-scsi 7456 0


and psaux | grep `fuser /dev/dsp/`
returned me
root 528 0.0 0.5 1404 464 pts /0 5 21:57 0.00 grep fuser /dev/dsp (i wrote it down because i dont have internet on that box its just for music nothing needed to work besides xmms the mouse and the sound 3 out of 3 lol xmms dont work the mouse didnt work i worked hours on that and now the sound ^^)

Try alsaconf as root, it should load the required alsa
oss emulation modules to use /dev/dsp

I am not sure if the following might work on your machine or not but it works on mine.

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alsamixer
make sure that the volume is what you want and the options are not off. if they are then click m for the ones you need.
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If the above didn't work for you then try to load the module yourself
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/sbin/modprobe soundcore
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If nothing worked then try running, alsaconf, as keefaz sggested.

i tryd running alsaconf as root normal user everything it says
command not found same for alsamixer /sbin/modprobe soundcore returned no error but i still get the error
i am gonna try to install the alsa package

I dont think slackware 8.1 has alsa try modprobe sb