If the protection isn’t too advanced, you can use DVDShrink in reauthor mode to select certain sections of the dvd. Use the Start/End Frames tool within Shrink to pick the exact part of the movie you want to save. This will give you a smaller dvd as output. No need to use Nero unless you want to combine several such sections into one dvd.
In that case you can convert the vob files found in your smaller sections to mpg using a tool called Vob2Mpg.
And if the protection found on your original dvd is too advanced for DVDShrink to handle on its own, you can rip to the hard drive first using DVDFab HD Decrypter, then open the files and work with them using DVDShrink.
All of the programs I have mentioned are free to use (except Nero of course)