I recently "recovered" around 30 PowerPoint files that I put together about 17 years ago. None were critically important; just some crude stop motion movies, homework, and other horrible "paintings", but they're a neat part of my childhood.
At they time, I had put them together using PowerPoint 2.0 (maybe 1.0, but I doubt it) and modern versions have long dropped support for those files. As I researched, I found that a straightforward conversion was impossible. There were specific conversion components for some versions (I think there was a v2 plugin for v3) and support for older formats seemed to be quickly dropped. By investigating installed files and old software reviews, I learned that v3 or v4 would do fine with the v2 files that I had and '98 or 2001 would upgrade the converted files to the "modern" binary format, it didn't look like 98 could read v1 or v2 files. Any of the more recent versions could upgrade those to the new XML format.
So I assembled my tools; I actually already had access to archived installation images for 2001, had installed 2008, and amazingly still had floppies for v4 and even found a *nix box with a floppy drive. I've previously played around with SheepShaver, but running the old Microsoft products proved to be difficult. I don't remember the exact issues, but installation or execution failed consistently when trying to run version 2001. A thread on the SheepShaver forums indicated that running under Ubuntu might be successful, but I didn't have any luck. I did find success running SheepShaver under Windows, and of course running 2008 under Mac OS X 10.6 was just fine.
In the end, my conversion chain looked like this:
10.6 > SheepShaver > MacOS 9.0.4 > PowerPoint v4 - v2 files to v4
Windows 7 > SheepShaver > MacOS 9.0.4 > PowerPoint 2001 - v4 files to modern binary data
10.6 > PowerPoint 2008 - binary files to XML
The only degredation I've noticed is that one file seems to either be using a font I don't have or perhaps the spacing or size was lost as the text doesn't quite line up correctly.
I suppose I should also take a pass through my other files and upgrade any Microsoft data to more modern formats, though nothing goes back as far as these did. Or just print them out to PDF. It's not like I need to actually edit any of these.
What strikes me most is how transient version support was even for Microsoft's own formats. I'd think at the least that Microsoft could keep a basic conversion product going for modern OSs and all the old formats. Not that I actually expect this from them.