dvd's use mpeg 2 compression, if you look at the file structure, in the video_ts folder, the files will show up as *.vob files.
Looking at the website for that mydvd program, I would say that it is burning the discs so that you can use it in a regular dvd player (i.e. as video).
you might want to try using nero to burn the discs as a data dvd that is useable in a computer.
link for the demoversion of nero
http://www.nero.com/us/nero6-ultraedition.php