You may have some trouble there, assuming you are running Windows. In order to legally decode the encryption on the DVDs, software developers have to pay to license the technology. This was at the root of the whole DeCSS thing, since the developer just wanted a way to watch DVDs on Linux, and no software developers wanted to pony up the bucks to license the CSS keys.
The MPAA etc., have tried pretty hard to keep control of that process, so there aren't a lot of legal, free software DVD players. Most drives come with a basic version of WinDVD or something similar, though.