adding subtitles to DVD

[namsilat]

I was going through one of the video guides on adding subtitles to DVD, but I could not even get by the first stage. When I load the DVD into DVDShrink under Re-Author mode, the main movie about 2 GB in size is not displayed at all. Instead, under main movie, a 384 MB commercial/trailor was displayed as a result. When I tried to load the DVD under Full Disc mode, this error message poped up:

DVD Shrink encountered an error and cannot continue.
Invalid DVD navigation structure

Any ideas?

[KameleOnOff]

The problem look like an authoring errror or an Arccos protection. Try ripping again with DVDFab Decrypter.

[namsilat]

The DVD is a ISO file from somewhere else, so I am not sure if there is any authoring problem. I used DVDFab Decrypter, after which I tried DVD Shrink again, but still showed no main movie.

I noticed while watching this DVD with PowerDVD, that it starts with Title 2, then Title 3, then back to Title 1. Title 1 is the main movie. Title 4 is the commercial/trailor. Is that unusual?