Power Point presentations will not work on websites. The person either has to have Power Point on their computer or one of the power point readers installed on their computer.
There is a work around though.
http://camstudio.org/
This little program is a Screen Capture software. So, install CamStudio and then fireup the power point presentation. Start the Cam Studio to capture the screen and then stop it when it is done. IT will , if I remember correctly, save it as a wmv file of which you can upload to your site.
Hope that helps. I have created many video turorials with this and it works well.
Andy