If you are not hearing _any_ sound at all (like mp3s played through xmms or videos through xine) your driver might be misconfigured.
It was this way with my Audigy card.
This is what helped in my case:
o) open up the console
o) su to root
o) issue the "harddrake2" command & press enter
o) wait for the detection of devices
o) find the Audigy card and select "Configure Device"
o) change the Driver to "audigy"
o) quit and restart
While rebooting you should hear a cracking sound when the card is initialized.
After reboot, start up a mp3 or video player and check if you hear any sound.
Make sure you turned up to volume! (Yeah, you never know...