I advise you to rip DVD's to ur computer or other devices like iPod/Zune ...This will help to prevent losting or damaging DVDs . I will recommed u two tools to backup DVDs:
Handbrake(Free): http://handbrake.fr/
If you just rip DVDs now and then or have no special requirements like editing, adjust parameter for DVD Movies. Handbrake is quite qualified.
Daniusoft DVD Ripper software: http://daniusoft.com/dvd-ripper.html#135
DVD purchased or rented from stores have copyright protections. You can try this Daniusoft dvd ripper, it is able to rip dvds to computer in 1:1. it is also capable to save dvd to computer in regular video format. it can bypass all kind of dvd copyright protection schemes, so it is able to rip copyright protected dvd movies.
Not like some ordinary DVD rippers, it will not break the video into pieces, it will join all DVD titles and chapters and make them as one standalone video file, thus you can play it on your USB drive.