PowerPoint XP presentations can be opened up in PPT 2000 or PPT 97 and run
easily. However, if you used any of the new features (animations), they
will not animate, instead those objects will (from what I've seen) just
appear on the slide when it comes up. If you want to make sure they work
seamlessly, click "Tools", "Options", click the "Edit" TAB and uncheck the
bottom three options.