Open Question: i'm having a problem with my computer audio?

okay, so my computer will make noises saying that something cannot be performed or whatever, but it wont allow music to play through itunes, or youtube. it wont announce when i have received an instant message/email either. everything is plugged in and turned on, when i click on the volume icon (bottom right of the screen) it says that "there are no active mixer devices available". it then instructs me to go to control panel, then to "add hardware but when i do this, it all leads back to the instructions telling me to go to the volume control (which i cant open in the first place) anyone have any ideas on what i could do?