The software is limited. If I cannot use the software, How can I make a
decision whether I want to purchase it?
The trial is time limited, yes. You install it, you activate it, then you
use it during the time allowed. Activation is done through the Help menu
option in 2003 and older, or through Office--> PowerPoint Options, Resources
in 2007.

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Kathy Jacobs, Microsoft MVP OneNote and PowerPoint
Author of Kathy Jacobs on PowerPoint
Get PowerPoint and OneNote information at www.onppt.com
I believe life is meant to be lived. But:
if we live without making a difference, it makes no difference that we lived
> The software is limited. If I cannot use the software, How can I make a
> decision whether I want to purchase it?