1. close ALL sound apps including gnomes mixer applet and you may have to close xfce4
2. run this command to list all sound app's using sound card: lsof /dev/dsp* /dev/snd/*
3. all sound apps and mixers closed?
4. as root or sudo run this command: rmmod snd-  (ask which snd- module to use)
5. report any errors from that command?
6. if no errors from the rmmod command then...
7. as root or sudo run this command: modprobe snd- model= (ask which snd- module and model to use)
8. report any errors from that modprobe command?
9. if no errors then run: alsamixer   and check the mixer settings, and unmute and set volumes
10. report any problems unmuting alsamixer controls and setting volumes
11. run this command: speaker-test -c2 -Ddefault -twav -l1
12. report no sound or errors or if you have sound