Preview Slide Shows in MS Powerpoint
For a quick preview of a slide show while you're editing a presentation, hold down the CTRL key while clicking View Show on the Slide Show ribbon. Instead of opening in full-screen mode, the presentation, starting with the current slide, appears in a small window over the slide being edited. To edit the slide and see your changes in real time, align the Microsoft Office PowerPoint window so that the preview slide is in view. Any modifications that you make appear in the preview window.