unable to do voice chating on yahoo messenger...warning comes as "computer's audio input is already in use by another application". ...

Did it ever work?

This is often caused by something else being plugged into an input, or multifunction jack - such as surround speakers.

Will need specifics about your hardware and OS before we can move on.

other functions are normal such as voip call..

desk top...using windows xp

Well, if other programs work, then the hardware is good, so I don't know since I don't use Yahoo chat. You might check out Yahoo Messenger Voice Chat Problem | Microphone Does Not Work With Yahoo Messenger | Call Setup For Yahoo Messenger