Sound problem with nforce2

[Kobalt]

Whenever my friend uses his microphone in counter-strike or voip programs like ventrillo, the sound is played through the mic to the other people as if he has speakers. He has headphones however, so the mic should not pick up any backround sound generated by the headphones. It is impossible that the mic is picking up sound from the headphones, because he has had this headset with many different computers without the problem. Im quite stumped on this one, as I do not have his computer infront of me, which makes things difficult. Is there specific setting for this? help :D

His specs
qwerky Asus A7N8X-VM/400
Onboard gfx
mcp sound
windows xp
Nforce 4.24 drivers

[STEvil]

If his mic is part of the headphones then one of the wires inside the cord is shorting out to the mic probably.

It is also possible there is a screw grounding a trace or something inside the case.

Those are the two most likely to me, unless he has something configured incorrectly in the sound drivers.