Hmm..
First question that comes to mind is why you want to get it back into the camcorder? With a decent editing app (which Ulead may not be), you should be able to do anything you like in the computer, then output to DVD, VCD or even VHS.
You might try a shareware program like Blaze Media Pro 5.17:
http://downloads-zdnet.com.com/Blaze-Media-Pro/3000-2194_2-10342979.html?tag=lst-0-2
It claims to handle nearly any type of video file conversion. Keep in mind that codecs are generally proprietary and such programs can only use codecs that are installed on your computer.
I quickly checked Sonic's MyDVD program's help file and couldn't find anything about file conversions, so that's likely not a solution.
For help with a specific codec issue, try:
http://www.moviecodec.com/
Good luck.