Does anyone know how I can make my computer play ...

You'll need a dvd player like WinDVD or additional video codes (if you already have a compatible player).

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. 

It involves changing the regional settings on your DVD drive, but I would be VERY careful about that. You can usually change that only once or twice on a computer. Once you hit the limit there is no way to change it again.

Even reformatting your hard drive will not wipe out that information.

This link will give you more information. Be careful!