First, all caps posts are not pleasant, stop yelling.
Second, we need a little more information. Can't play MP3s while true, doesn't tell us anything. Can't play mp3s in XMMS, NoAtun, etc, that gives us a starting point.
CDs - check to see if the thin cable is connected to your sound card. It is required.
MP3s - what prog are you using?
Mixer - Open your mixer and make sure that all levels are turned up.
Under configuration - Does your sound card show up, does the test sound play?
Documentation - Have you been through the help files that came with/are installed with your system on configuring sound?