Many computer media players will not play back a complete DVD movie,
but as you found, it will play individual VOB files, which is not much
fun because you have to select a new VOB file several times to
complete a whole movie.

I use Cyberlink PowerDVD in a fairly recent version to play an entire
movie on the HD. You just have to go to the file where you have the
movie DVD files stored, right click on the icon for the whole movie,
and select to play with PowerDVD from the list of players that comes
up or by selection from other programs that can be brought up if
CyberlinkDVD is not on the list. There really is little need for
playing back whole DVD movies on the HD. With a commercial movie now
usually on a DL disk and running up to over 8 GB in size, it would not
take many movies to fill up the HDs on many computers. If you have DVD
movies on the HD, the best thing to do is to burn then to DVD. Blank
DVD discs now cost less than the price of a US first class postage
stamp when you buy them in 100 lots. If you want to store many DVD
movies and play them from a library, you need a DVD server now used
for some high end home theater systems. These are still very costly if
the can store and play a large number of movies because of the massive
banks of HDs needed to store all of the movies.