Is it legal to rip a DVD to a computer if you already own it?

you betcha

Technically yes, due to the fair use( http://www.copyright.gov/fls/fl102.html ). However as the MPAA would see it possible no.

I agree with muddyh20 as well

“i swear, all those movies on my computer, i used to own the dvds for all of them but they got scratched and ruined so i couldnt play them anymore, but thankfully i backed them up first, and since they couldnt play, i just threw them out, along with the reciepts.. of course im not lieing.. and i definately didnt download them”

So if we payed for the rental, does it also make it legal to back-up the movie on our computers before we return them?

@g33s: no, because the law provides for making back up copies of things you own, not things you rent.

Muddy and deathfrombelow are definitely wrong on this. “Fair use” only covers use for purposes of “criticism, comment, news reporting, teaching, scholarship, and research.” It isn’t at all a settled doctrine of law as the link to the copyright office shows. I mean, I’d certainly not worry too much about backing up a DVD you know. The MPAA isn’t going to care as far as I can tell. But it is also in the MPAA’s interest to not cede any ground. A copyright grants the owner rights to all forms of reproduction. So, say the MPAA decides it wants to start selling movies as .avis (why it didn’t decide this years ago I don’t know) then making a copy to your HD as an .avi is definitely a use that effects the potential market for or value of the copyright. The simple fact is that copyright law is not at all suited to deal with digital media and copyright law is all there is to go by. Until there’s some definitive Supreme Court rulings (and the Supreme Court doesn’t rule on things like this) or Congress changes the law, it’s going to be piecemeal application of 17 U.S.C. §§ 107–118 that varies state by state.
That said, you shouldn’t worry about copying DVDs to your computer because it seems very unlikely any court would care about that.