sound problem

hey everyone, I'm coming across a really weird problem. on programs like GAIM, progams that are supposed to make little sounds, they don't happen to work. I mean, I know the sounds are annoying, but I don't want anything to not be working on my box. also, when i play cd's, it reads, and plays, but you don't hear anything. but it's weird, because my xmms player plays my MP3's just fine. any suggesstions to solve this problem ?