It will play, but it will not be able to take use some of the features, such
as the newer animations. If you plan to create presentations using 2003 for
2000, you can disable the new features. Go to the Tools menu and choose
Options. On the Edit tab, check the boxes under Disable New Features. This
will allow you to use 2003 to create presentations that will play properly in
2000. Of course, it means, you can't use some of the nice new features.
--David
David Marcovitz
Microsoft PowerPoint MVP
Author of _Powerful PowerPoint for Educators_
http://www.loyola.edu/education/PowerfulPowerPoint/