Hi,
PPTFaq.com has an article on this. I think you might want to try a different MIME type, as they have mentioned in their article.
If this PPS is going to be linked to on a public website, I wouldn't go about it this way because for PPS to work the PointPoint Viewer or PowerPoint must be installed. A lot of people don't have PowerPoint so unless your target audience is almost guaranteed to have it, you might want to look at creating a video from your PowerPoint or save it as HTML.
HTH,
Joe D.