Oval shaped movie in powerpoint

[addisondesign]

Hi, Firstly I work on an apple mac. I am trying to acieve an oval shaped slide show with transitions which runs as a loop in the bottom corner of a web site and also in a powerpoint presentation. I created a movie in imove from individdual photoshop jpegs but it always appears as a rectangular box in powerpoint. Does anyone know how to achieve this in powerpoint or if I need to create the slideshow/movie in a different format to make it work???

HELP
G