A couple of full proof ways:
Use an A/D converter to capture directly from the DVD playing to the computer.
On the software side, get a copy of
TMPGEnc Express.
There is an easy wizard that will allow you to export the entire DVD to a single AVI uncompressed file. It will even extract the menus and subtitles for you. I've used this software countless times and the results are excellent.
Vince Becquiot
Kaptis Studios
San Francisco - Bay Area