Correcting sound inbalance from a capture

Hi, I have just captured from my vcr a documentary that takes, in raw avi, 60 gb on my hard disk. I’m about to transcode it into MPEG 2. However, due to my own ineptitude, when I captured the documentary I forgot to plug in one of the wires into my canopus advc 100 and, consequently, I only have sound coming out from the right channel (every thing else is fine). Does any one know how I can transcode or author this file so that the sound comes out of both channels - I have nero 6.6 and tmgenc plus.
Many thanks,