Hi Mark- What you really want to do is two things:
(1) Get a cpy of VideoLan's VLC Player from http://www.videolan.org/vlc/
The player is available for a number of platforms including Mac OS and Windows. And it doesn't bother with the region code limitations as commercially purchased software does. The product is actively developed, and has a pretty good feature set;
(2) Turn OFF autoplay for DVDs
Most computers have an option for autoplay. It makes it so when you just stick a DVD in, that the system reads and recognizes it, then loads the proper application. Well, for a number of computers, before the determination of which application to use, it also checks which region the DVD is viable for, thereby preventing it to play, even if you have a viable application to play it. Turn off autoplay, ad select the player manually.
This is especially true on a Mac, but probably viable for Windows, and not important on Linux.