software

I've developed some financial planning spreadsheets in Excel that I believe
could be a saleable product. I'm looking for resourses to learn how to
address issues like:
1. Is it possible to quot;registerquot; spredsheets to a computer to prevent people
from giving away copies?
2. What's the best way to determine the minimum Excel release level required
to run my spreadsheets?
3. I have attempted to show others my spreadsheet on their computer and
recieved errors in the spreadsheet that I did not see on my computer (even at
the same Excel release level). I can't imagine why.
Specific answers are welcome, but I'm really looking to be directed to some
resources or a more appropriate community that deals with Excel spreadsheets
as a product. Any ideas?
--
Steve