If you open your presentation in slide show mode and press F1, you'll see a
couple of keys that you can press that will pause your presentation. B will
give you a black screen and stay in that state until you press any key or click
the mouse. W will give you a white screen and stay in that state until you
press any key or click the mouse.
--
Sonia Coleman
Microsoft PowerPoint MVP Team
Autorun Software, Templates and Tutorials
http://www.soniacoleman.com