Quote Originally Posted by Cid
How would plugging headphones in a headphone jack be anything like a mic?

Do they sell mics that have no line or code, just a straight 1 or 2 inch mic coming out of the port?

You plug them in the mic jack.

Headphones : electricity -> magnetic field -> vibration -> sound
Mic: sound -> vibrations -> magnetic field -> electricity.

Quality is poor, but it works.

As for integrated mics, clout is most lilely right about it being muted. If the speaker is not in your tooltray, it's in control panel -> sound options.