is there a built in microphone becuz when i talk to people online they can hear the music im playing but not me when i speak and the music is off

Would depend on the computer I guess. Mine has none.

What is the make and model of computer?

What program are you using to talk?

Are you using an external mic that is not working?

im using it with AIM and its a windows Xp idk what else its a dell hmm idk what else

What is the exact Dell make and model e.g. Dell Dimension 4200

You are using a voice feature of AIM?

Not a Voip service?

Are you trying to use an external mic? A headset? What device are you talking into?

Have you checked your mic settings via start > Control Panel > Sounds and Audio Devices > Voice