When you open or create a PowerPoint slide, it defaults to landscape, so contents display horizontally on your page. You can rotate the slides in your PowerPoint, letting the contents display vertically instead. Microsoft PowerPoint automatically shifts and resizes the contents of your slide to accommodate the new layout. The orientation you apply to the slides is also applied during the slideshow. You can rotate the slides before or after they are created.
Open the slide in PowerPoint 2007.
Go to the "Design" tab.
Expand "Slide Orientation" in the "Page Setup" group.
Choose the orientation you want to apply, "Portrait" or "Landscape."