Unfortunately, PowerPoint hides the actual file, which is called blank.pot in 2003.
In PowerPoint 2007, right-click the Office Theme image and choose Apply to Selected Slides. Instead of clicking the image of Default Design.pot, click its down arrow and choose Apply to Selected Slides. To remove the current template for one slide in PowerPoint 2002 or 2003, select the slide in the left pane, and then open the Design task pane. In PowerPoint 2007, choose the blank slide from the Themes group of the Design tab.
