Are you using an 845 Chipset? Visit www.alsa-project.org
and download the alsa rpms for the onboard sound card.
Install on your system and follow the instructions on the
alsa site.
Add the following lines to /etc/modules.conf after installing
the rpm:
alias char-major-116 snd
alias snd-card-0 snd-intel8x0
alias char-major-14 soundcore
alias sound-slot-0 snd-card-0
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
After that at # prompt, type following commands:
# amixer set Master 80% unmute
# amixer set PCM 80% unmute
# amixer set CD 80% unmute
# amixer set Headphone 80% unmute
Try playing a sound file.
To make above permanent, you can add it to
/etc/rc.d/rc.local.