Do you mean that sound works in other distributions? Anyway, type
lspci | grep snd in a terminal, if there is output, your sound card has been detected, try to see if it is unmuted by using
alsamixer.
If your sound card has not been unmuter, try to find the module for your sound card at
www.alsa.org, and run
sudo modprobe <module name>.
Also try
sudo alsaconf.
And see this - *wiki.ubuntu.com/SoundProblemsHoary
Search the forum, there have been many sound related problems posted.