Okay understand that other sounds, but not your voice, are still being picked up.
Do you hear the same sounds in your headphones/headset as your friends do?
What sound card are you using and what all is plugged into the various 1/8" (3.5 mm) ports on the sound card and motherboard. Verify that you are using the correct ports and connections.
Again try the mic and headset on another system. See if the problem follows the mic and headset.
If not, go into Playback devices and Recording devices per my original post. There are some configuration settings controlling how various sounds are managed. Look at the properties and any "Advanced" tab settings.