DVD Decrypter and DVD-TO-MPEG, the dvd decrypter will copy the disc on to you'r HDD, the DVD-TO-MPEG V2.0 will turn into.. well, mpeg.
I dunno how that program works though (the 2'nd one)
If you wish to copy a DVD Movie into you'r computer as a whole you won't be needing it anyway, if you want however to burn those dvd's into another dvd-cd then DVDShrink is you'r BEST option, I use it for that stuff its great and totaly free.
DVD Decrypter if you want to copy DVD's as a whole DVD onto you'r HDD.
DVD-TO-MPEG V2.0 if you want to turn the DVD's you copied into you'r HDD into an MPEG.
DVDShrink if you intend to burn those DVDs into discs without converting them to anything (So they will remain a DVD-format movies) - for this program you don't need dvd decrypter, its a standalone program.
It sucks because you have to compress the dual layer DVD to fit on a single layer DVD, so there is a loss in quality. Depending in how high end your equipment is, and how picky you are when it comes so quality, you may notice a difference, you may not.