I'm not going to go look for links that document this, sorry.
You're welcome do download converter packs and such if you want, but they're
not necessary.
Oh, I guess you could look at the File | Save as option. There's one for PPT
97-2003 AND 95. That's because PPT 95 has a different file format than PPT
97, 2000, 2002 and 2003. So you need that option if you want PPT 95 users to
be able to open your file. Otherwise, the PPT file is just saved as a
presentation, which is openable by 97, 2000, 2002 and 2003 -- because they
all use the same file format.