the iPhone's heaphones have the headphone and microphone signal all going through the same plug, but your PC has a separate inputs for the audio out and the microphone... so you would need some sort of adapter that would split your iPhone headphones into two plugs: one for the standard stereo headphones, and one for the microphone. I guess the thing you need would be something like 3.5mm to 2.5mm adapter with a headphone plg too... there are adapters that do the opposite function, so it may exist... i'll have a look.
I think the original poster just wants to use the mic part, right?
The problem is the iPhone earbuds have a 4 conductor plug (common ground, left, right, and mic) where the mic input on your mac/pc is a 3-conductor jack. The earbud plug is designed to be backwards compatible with 3-conductor stereo headphone jacks, but the wiring for a mic input is different.
You might get lucky by pulling the plug halfway out of the jack or somewere in between.... you might get the right combo of conductors to connectors and get a mic signal flowing. But I kinda doubt it.
you know i actually heard that if you put any earbuds like the ones you have into the microphone input on your computers and you just talk into the earbuds itll work like a microphone. im not kidding lol try it
yeah i just tried it and it worked but you gotta talk louder