You might want to look here
http://officeone.mvps.org/powershow/powershow_ticker_show.html Or here is a
method for a two slide, slide show
First you need to create the text you wish to use, then animate the text,
crawling from right - by letter - timing automatic 0 seconds after last.
Position the text to the left of the slide so that the first & last thing
you will see when running the presentation is a blank slide. Next, create an
exact copy of this slide and allow for automatic transition after 0 seconds.
Set the 2 slide show to loop continuously, run the slide show and enjoy!
To see which version of PowerPoint your using, Click on Help, and About
