Do you want to simply back up the files to disk, or do you want to watch them on a stand alone dvd player?
There are a lot of free conversion programs that can take the various file formats and output to dvd-video. DVDFlick, FAVC and AVStoDVD spring to mind. All are free. You can burn to disk with either Nero or Roxio, or use an excellent free burning program called ImgBurn.