So, the 'right' half of my pair of headphones broke (the transducer+wire are fine, but the earpiece broke on the headband and so the earpiece won't sit over my ear). So now the right channel is being broadcast to my cube neighbors when I wear my headphones. Yes, they look very silly.

Is there a way to ensure, in Windows XP (or Windows Media Player), that all stereo sound is downmixed to the left channel only (ie, in mono) so my neighbors don't hear my music? I know that I can setup the mixer to set the balance to 100% left, but information in the right channel won't be heard.