Better if you use Nero just for burning.To find a video converter just Google video converter and the list is big enough to find the right one.
WinAvi is very popular but they work on a new one v7.0 so is VSO DivX to DVD was freeware now is not for free anymore also
Cucusoft and so on.Convert the file separate and if you have a video ts folder use for Nero only the vob’s files.Clone DVD 2 works faster with the video ts folder same VSO Copy to dvd.The trial version of any converter may watermark your file.To find out the right convertion first open your avi with GSpot and be sure the file is ok picture and sound and after that make the convertion from Xvid or Avi or Mpeg or whatever is your file to dvd.Good Luck.