I'm pretty sure the message:
kmod: failed to exec /sbin/modprobe -s -k scsi_hostadapter, errno = 2
comes from having scsi emulation on your cd-rw. The system thinks that because you've got a scsi device, it needs to load the scsi adapter module. I get the same message - I don't believe it cause any problems.
As for sound, Slackware 9.1 uses the ALSA sound modules abd tries to automatically detect your card and install the correct modules. If you do an 'lsmod' command from a console, do you see any sound kernel modules loaded? You should see stuff like:
snd-pcm-oss 37252 0
snd-mixer-oss 11992 0 [snd-pcm-oss]
snd-via82xx 11712 0
snd-pcm 55904 0 [snd-pcm-oss snd-via82xx]
snd-timer 13252 0 [snd-pcm]
snd-ac97-codec 37240 0 [snd-via82xx]
snd-page-alloc 6004 0 [snd-via82xx snd-pcm]
snd-mpu401-uart 3136 0 [snd-via82xx]
snd-rawmidi 12512 0 [snd-mpu401-uart]
snd-seq-device 3920 0 [snd-rawmidi]
snd 27460 0 [snd-pcm-oss snd-mixer-oss snd-via82xx snd-pcm snd-timer snd-ac97-codec snd-mpu401-uart snd-rawmidi snd-seq-device]
soundcore 3332 4 [snd]
but instead of the via82xx you should see some module relevent to your sound card. If you don't see anything like this, maybe ALSA doesn't support you sound card? You can check the supported hardware list on the
www.alsa-project.org website.
If you do see these modules then - have you turned up the volume? It's off by default.
Run 'alsamixer' from the command line to set volumes and then 'alsactl store' to save the sound volumes.