Shrink can do it if you managed to get the IFO, BUP and VOB's for the movie by using DVD Decrypter.
Load Shrink and go straight to reauthor.
Then go to the folder where the movie is. It should come up something like title 1.
Drag the title over and it analyses just the movie.
It should then backup.
Otherwise use ifoedit and create new ifo's for the vob files. Use this guide.