Problem:


Powerpoint won't open an OpenOffice (impress) presentation file.

Fixes:


Convert presentation format with Openoffice


Powerpoint doesn't understand OpenOffice Impress format (.odp).
Use OpenOffice and save the presentation as Powerpoint format (.ppt)

Convert presentation format with google


Login with a google account at doc.google.com and upload the presentation. Then export it as PowerPoint format.