audio mixdown to mp3 turns to mono

I record one track panned all the way left. Then I record a second track panned all the way right. At this point everything sounds fine one instrument on the left and one on the right. I then audio mixdown to an MP3 and when played back through windows media or anything it sounds mono, no separation at all. Anyone know what I am doing wrong?

Hi,

Make sure, the Mixdown is not setup so the file is exporter to the mono file.