Have you tried the youtube downloader? and saving it as Mov / AVI?
PowerPoint Supports
•avi:
◦Supported
•flv (Flash) :
◦Flash is not natively supported, but can be accomplished with the aid of directions from Macromedia
•mov (QuickTime) :
◦Supported up to version 3 on Windows
◦Subsequent versions not supported on Windows
◦All versions supported on OS X
•mpg:
◦MPEG1 is supported
◦MPEG2 is supported on Vista only and may require a 3rd party plugin on XP or OS X
•rm (RealMedia):
◦Not Supported on OS X or Windows
•wmv (WindowsMedia):
◦Supported on Windows
◦Supported on OS X with the Flip4Mac codec