VLC, at http://www.videolan.org has what you need.  I'm uncertian about 
the region changes, I use dvddecrypter to copy the dvd to my system 
(ISO) removing CSS, region encoding, and macrovision in the process and 
then play it from my computer.  The main reason, though, is to keep my 
kids fingers off the DVDs - store lots of dvds on the hard drive, never 
need to touch the actual dvd, but I keep them safe since I use cheap HDs 
and they tend to fail after a few years.  Daemon tools will allow you to 
add a virtual dvd drive to the computer that 'loads' the ISO disc as if 
it were physically present in a dvd drive.

There are utilities that allow unlimited region changes, but I haven't 
needed one in awhile so you'll have to use Google.

Good luck!

-Adam

Alan B. Pearce wrote:

>I will hijack this thread slightly if I may.
>
>Looking for a program that will allow me to play a DVD on a machine that has
>a DVD drive, but no appropriate software. I assume one of the programs
>listed on this thread will do it, but interested in any others.
>
>Nice features to have would include unlimited region changes, and ability to
>deal with widescreen video.
>
>  
>
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