I think I've done this before but have forgotten the magic trick.

I have a file with two tracks of audio that shows as a single stereo track (It's really just two separate tracks)

How can I split this into two separate tracks?

Jim, you can right-click on the audio track > channels >choose left or right channel.

Jim, you can right-click on the audio track > channels >choose left or right channel.

(and duplicate the track)

If you have a pro version of Vegas, there's also a free "stereo split" script on my website so you can do this with the click of a button.