First you need to check if the correct driver has been loaded.
open a terminal and type: su root
this command logs you in as administrator
once you're logged in as root type: lsmod
this will show all modules (drivers) that the linux kernel has currently loaded.
According to the official documentation available here: http://www.alsa-project.org
the name of your sounddriver is: snd-via82xx
Check the list to see if it is there.
If it is in the list your problem probably has to do with the volume setting. The sound system sometimes defaults to zero. A detailed volume setting can be seen by typing: alsamixer
If it is not loaded you can try and load it manually: modprobe snd-via82xx
If it loads successfully ( i.e. no error message) run alsamixer to check the volume.