Everyone else gave you the most likely answer, but one other possibility is
that slides 1 through 83 are hidden. If that is the case, go to slide
sorter view, select slides 1 through 83, go to the Slide Show menu and
choose Hide Slide. If a slide is hidden, you'll see a greyed out slash
through the slide number.
--David
--
David M. Marcovitz
Microsoft PowerPoint MVP
Director of Graduate Programs in Educational Technology
Loyola College in Maryland
Author of _Powerful PowerPoint for Educators_
http://www.PowerfulPowerPoint.com/