You can always use DVD-shrink (
http://www.dvdshrink.org/what.html)
DVD Shrink is a freeware program to make legal copies of dvd's that you own for backup solutions. While it's intended to burn them afterwards on a single layer dvd it first creates the files on your hard disk in very good quality. (large size)
If this is not what you want you are maybe thinking of ripping.
Then Google can be your friend: please have a look at
http://tinyurl.com/4rutm for various resources.