Powerpoint:mac X


I am trying to make multiple master slides within one presentation. I have followed some of the instructions that I found for PowerPoint 2003, but they don't seem to work. When I go to View > Master > Slide Master, there are no thumbnails therefor I cannot duplicate a slide...it seems simple enough but I cannot get it to work.
I know that you can add new Slide Designs, but I would like to just make masters within the pp presentation and not have to have those extra files.
Thank you in advance for your help!!!