PowerPoint presentations are not supported by Multimedia Manager, and cannot be streamed as a presentation when posted to the website. Even when saved as .MOV files with PowerPoint's "Save As Movie" command, presentations lose their transitions and custom animations when uploaded and viewed on a website.
Publishing a link to your presentation
The easiest way to distribute a PowerPoint presentation would be to upload it to File Manager, and then post a link to the file on a webpage. Users would be able to download a copy of the file and view it on their own computers, provided they have a copy of PowerPoint. This would allow you to preserve any custom animations, slide transitions and timing in the presentation, but the presentation itself would not be displayed on the website.