Try Windows 7 Codec pack Windows 7 Codec Pack
. WMP does not have all necessary codecs.
Vlc should be able to play the movies which leads me to believe that the files may be corrupted. Use Medianfo to determine if the files are corrupted: MediaInfo - Download.
You should see a video stream and one or more audio streams. Upload a screen shot if you are not certain.
VTS_01_1 VOB is already in dvd format so why would you be trying to convert that one to dvd?
What are the file structures of the movie files you are trying to play (ie .MKV, .AVI, .MP4,etc)?