Hello Goddess!
It's rare that I get the opportunity to interact with a true godess, so
this pleasure is all mine!
"won't run on their machines" leaves a lot unsaid.
Is it that the Macs have PowerPoint and your presentation won't play?
Certain parts don't play? More info is needed to troubleshoot this scenario.
Is it that the Macs don't have PowerPoint at all? If that's the case,
for Macs running OS9 (pretty old by now) there's a free Powerpoint
viewer. It plays presentations that have all of the PowerPoint 97
features, but nothing later (like path animations for example). For OS X
macs there are several flavors of free OpenOffice that makes crude
reproductions of Microsoft Powerpoint presentations. Newer Macs can use
a 30 day free trial of Microsoft Office 2004, but after 30 days they
will have to purchase the product (PowerPoint is available separately if
that's all they need).
-Jim Gordon
Mac MVP