Free Sequential Save Add-in by Shyam Pillai
Problem
You've worked on a presentation for hours. Then it hits: there's a power glitch, there's a computer glitch, PowerPoint throws a silly fit, or maybe you do something a little odd. And you lose all your work. Your presentation gets corrupted, PowerPoint won't reopen it and none of the suggestions elsewhere on the PPT FAQ help.
Solution
You've already tried the suggestions here in the FAQ. If they didn't work, there isn't much else you can do but start over.
OK, so you don't really want to hear a lecture from us right now about saving and keeping backsup and all that ... but let's face it, if you'd done it, you wouldn't have this problem now. So please ... from now on:
Save. Early. Often. Under a new name each time, so you have a trail to follow back to an uncorrupted version of your presentation.
That used to be a nuisance, but thanks to PowerPoint MVP Shyam Pillai, keeping a logically named set of backup files is no more difficult than clicking the Save button.
I'll hand the microphone over to Shyam:
The original idea came from Austin Myers, PowerPoint MVP who made a request for this add-in. The basic idea is to create a backup of your file every time you click on the Sequential Save button. The add-in will add a button to the Standard toolbar adjacent to normal Save button, every time you click on that button, the add-in will create a backup of the last saved version on the disk and then will save the existing file. The add-in actually opens the presentation on the disk and then saves a copy under a different name depending on the options chosen by the user. You can either create a single backup file or multiple sequential backups. The add-in does not delete any presentation nor does it change the original presentation in any manner.
Shyam's Sequential Save add-in is free. You can download it here.