Tutorial on Making an Automatic Slideshow and Delay Before Slide Advances
http://www.freewebs.com/pptheaven/tutorials/SlideDelay.html

Tohlz, Shawn
PowerPoint Heaven
2005

Abstract:

You need to make some delay so that all your slides will pause for a while before going to the next one. There are few ways to achieve this. This tutorial will cover two simple methods.