Puck,
You can turn your Mic off so it will not playback through your speakers. Double click on the speaker icon on your sys tray to open your Play Control. Click the mute button on your Mic.
If you don't see your Mic, click on Options/Properties. You will see a bunch of check boxes, check the Microphone box then OK. You will also see buttons for Playback and Recording. You want to select Playback. Only mute the mic in Playback and you shouldn't hear yourself over the speakers.
Gunner