How can I redirect sound coming in from the mic to the speakers output
Solution 1:
In Windows you should be able to open the mixer, and ensure the Mic is available (and not muted) for playback. Usually it IS muted for playback by default to prevent feedback.
You may have to adjust the options of the mixer to actually show you the Mic's playback volume slider/mute button:
In XP you can do this in the Windows Mixer via the Options menu.
In Vista check Control Panel-->Hardware and Sound-->Sound-->Manage audio devices, go to the Playback Tab, select Properties. In the Properties window, pick Levels to adjust volume and mute for the Mic.