PowerPoint 2000 FEATURES not supported in PowerPoint 97
There are several new features in PowerPoint 2000 that aren't available in PowerPoint 97
Though both versions of PowerPoint share the same file format, PPT97 doesn't necessarily support these new features.
Since the PowerPoint Viewer, even the one that came with PowerPoint 2000, is actually a PowerPoint 97 Viewer, it has the same limitations as PowerPoint 97.
Here's a quick summary of what's new:
Auto-fit Text
Adjusts font sizes slightly in an atttempt to fit text in a bulleted text placeholder to a given space. Autofit information isn't saved with the file, so it will most likely be ignored in PowerPoint 97.
AutoFormatting
AutoFormatting in PowerPoint 2000 can include font changes. According to a Microsoft document discussing new PowerPoint features, "This is different from Microsoft Word 95 and 97's Autoformatting feature, which can change the font." Now if someone would explain that to me ...
They go on to explain how 1st gets converted to 1_with_superscript_st, how some fractions get converted to true fraction characters rather than e.g. 1/2. These seem to appear correctly when opened in PowerPoint 97.
Graphical and Numbered Bullets
PowerPoint 2000's Bullets and Numbering dialog is a great deal like Word's now. You can also choose your own preferred bullet character or use pictures for bullets. To quote MS again, "If you open a PowerPoint 2000 presentation in PowerPoint 97, graphical and numbered bullets appear as plain bullets. Numbered bullets appear as the default bullet defined in the slide master. Graphical bullets appear as the bullet characters used immediately prior to switching them to graphical bullets." OK, MS. You've redeemed yourself. That was a lot clearer.
PowerPoint Table Editor
PowerPoint 2000 features a built-in table editor very similar to the one in Word. These get converted to a group of AutoShapes when you open the presentation in PowerPoint 97. In fact, if you ungroup the table in PowerPoint 2000, you'll get a pretty good idea what will happen to it in PowerPoint 97.
Animated GIFs
Are supported in PowerPoint 2000, not in PowerPoint 97. PowerPoint 97 displays the first frame of the animation as a static image.
There are other inconsistencies between PPT97 and PPT2000. See PowerPoint 97 vs 2000 incompatibilities for more info.