Well the only drive that ImgBurn picks up only reads dvd's - doesn't burn to them. It will read and write cd's but if you want to convert the avi to play on a dvd player you'll need a drive that also burns to dvd's.
but i have downloaded movies on limewire an burned them to dvd using nero. so i dont know why nero wont burn the torrent files to dvd
ImgBurn also doesn't show you having a dvd burner so this may be part of your problem. Is the burner internal or external? Do you see it listed in 'my computer'? What's the make and model of it?
hmmm odd one, ok so you say you burned to dvd before? is this converting say an avi file to dvd files and burning or just doing a data dvd with an avi say? but get dvd flick a free app and use that to go to dvd see what happens...