Depends on where you are plugging them into your Pc.
If you are using the two front 1.5mm audio inputs on a pc tower or case.
In windows sound manager it treats the inputs and output devices differently.
For example if you look in windows sound manager you should see two mics. when clicking on the record devices tab.
If it shows two in there, simply right click on one and set it as the default recording device.
Its likely the mic is set to the rear port or 1.5mm jack of the mobo, or vice versa at the front but you still have to switch the default playback and recording devices and set them in windows sound manager.
After that it should work.
I know it works because years ago I worked this out in the end.
Make sure the mic is not...