Audio Measurement with PC

[JoeDracula]

I am using HP-Compaq DC5850 desktop to run my Labview Application.

My application measures the Audio Input from MIC-In of PC.

I am facing a problem,which I am describing below.

When I am playing a Stereo mp3 file of 1KHz, The measurements are fine. When I disconnect any one channel( either L or R) some time the measurement is fine.

If Left Audio disconnected, Frq-R,Amp-R is proper (1KHz,1.1V) and  Frq-L,Amp-L is proper (1KHz,0.1V). This is OK

But sometime both channels are Reading  (1KHz,1.1V), which looks strange to me.

Is there any way to solve this issue? This occurs ONLY in HP computers. If i use the same application in Dell Laptop(Latitude D620) I am not facing this Problem.

Audio support for  these PC's are listed below.

HP==>HD Realtek

Dell==>SigmaTel