Hello... a PC microphone is a "Passive" device if it is has a "Dynamic element" in it... They could have put a switch on it but would cost $ and materials... instead you use a "software switch" VS a "hardware switch" for it... this is a example of Software saving $ and resources in the world. B )
it can be done in your Device manager... Sound panel... etc.
You could go to Radio Shack and get what you need to solder/mount a switch on it.