As far as I know, you can export your PPT file as an HTML slide-show. Look for it, because I'm 99% sure you can. Otherwise, you can actually post it on the web, and if the user opens it in a browser (not download it) they will view it through the browser, but not have any of your site layout there.
Personally, the best idea is probably to port it over to flash. Although it may take time, you can guarantee people won't steal all of it at once, and you can make it look as you want across all browsers and platforms.
~Brett
