Might want to be careful about mentioning downloaded movies. The vast majority on the torrents are copyrighted material, and as such, we are not allowed to discuss copying them here.
Now, if you own your own dvd and wish to remove some sections of the movie you can use DVDShrink and deselect certain parts, like foreign languages, and subtitles you don’t want.
To get rid of more, like extras, you can use a program like VobBlanker or DVDRemake. Or you can make backups with menus and the main movie only using DVDRebuilder Pro.