Resizing m2v

Ok, I finally made a successful dvd. One thing though, the video is stretched out from widescreen to fullscreen. Is there anyway to resize the m2v file back to widescreen without reencoding the original avi? (dont want to spend the 20 hours again)

When you author it, make sure you select 16:9 and not 4:3, that will bring it back in line.