I have been using a heaset for some time on Windows XP without issue. Every time I plug in the headset combo of both earpiece and microphone a box would pop up and ask if it was OK to accept the new device. I must have accidently clicked the “Don’t show me this again” check box. The internal microphone on my Dell D420 laptop is working fine but when I plug in a headset I am unable to use the microphone from the headset.
After awhile of searching I figured out what this was. I did actually turn off the pop up and by doing so the Sigmatel audio device would not allow it to work. So first you need to turn the pop up back on which is located in the Control Panel and named Sigmatel Audio. Double click on Sigmatel Audio in the Control Panel to have the Sigmatel Audio Control Panel open. As you can see in the below image the Sigmatel Audi Control Panel only has one configuration option which is to not allow or allow by checking or not checking “Allow Reconfiguration Pop Ups”.
SigmaTel Audio Control Panel: Allow Reconfiguration Pop-Ups
Assuming this was also your issue simply unplug and then plug back in your headsets microphone. This should trigger the “Reconfiguration Pop-up” to take place where you can configure the microphone of the headset. The “Reconfiguration Pop-Up” looks like the below image.
Audio System Event: Microphone
Select the Microphone and click OK. This should allow the headset microphone to start working again.