Check this out:
"Mix Portrait and Landscape slides in a presentation"
http://pptfaq.com/FAQ00042.htm
The tutorials are using PowerPoint 2002/XP or 2003 as example. But the
procedure should be more or less the same. Post back if you need more help.

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Shawn Toh (tohlz)
Microsoft MVP PowerPoint
Site Updated: Dec 24, 2006
PowerPoint Anime - Rewrite
http://pptheaven.mvps.org
PowerPoint Heaven - The Power to Animate
> I was using the PowerPoint 2007 for using portrait and landscape slide
> orientation in the same slide/