in order to use your speakers as a headset, open your Volume Control. Click Properties, and check "Recording". Make sure everything in the list is checked, and click Ok. Make sure "Select" is checked under the item farthest to the Left. Should be "Stereo Out" or "Stereo Mix". This will allow them to hear, what you hear.. as long as its coming from your PC.
to change it back to your microphone, repeat the same process, only check "Select" under Microphone.
use the help section next time.
/moved