Things You'll Need
Instructions
Take your Xbox 360 headset adapter cable, your Xbox 360 headset, and then connect the two via your headset&'s output plug and your cable&'s input plug.
Connect it to your computer by plugging the red (or pink) end into the pink "Mic in" port, and the green end into the green "Audio out" port. These ports can usually be found on the front of your computer case and also in the back on your sound card.
Open up your PC game or program that is compatible with PC microphones (e.g. a sound recording program or an online video game). You can use it the same as you would a regular headset.