You probably aren’t old enough to have talks from the 1990s that you want to open with Powerpoint, to grab old slides, to see how you did it back then, or simply our of curiosity. But if you are and you click on them, or slide them over the Powerpoint icon, you will discover that they won’t open.
There is a fix! it is called Open Office. I just tried it and it worked well for a 1998 talk about the wonderful paper wasp Polistes annularis. The talk wasn’t so wonderful, not wonderful enough to get me the job I was then exploring, but the material was great. What struck me most was how sparse it was on pictures. There were lots of graphs but so few photos of these lovely wasps or their field site. I wonder if that is just me or a general thing.
No doubt Open Office has lots of features. I just went for the one I needed, opening and using old Powerpoints.