I have many duplicate emails in my archives and saved mail boxes. I
would like to automatically find them and delete the duplicates
(saving one email in each set of equal messages). I would like a
free/inexpensive off-the-shelf solution or a VERY simply implemented
solution that is very clearly and completely documented. This is in
the Mail 2.0 application under OS X v10.4. I do not want to export to
any application and need a solution that operates on the Mail 2.0
mailbox as is.

Perhaps this will help. It has a free trial version

http://www.office-addins.com/-outlook-addins/duplicate-email-remover.html

KauaiDawn

Thank you. Unfortunately that appears to be only for Microsoft Outlook
(no version for MAC Mail). Thank you though!

I used the applescript found at
http://www.macosxhints.com/article.php?story=2005050314315464&query=mail_dupes
to get rid of my dupes the other day. Worked great. Just set it off
selecting the dupes and then simply move or delete them once it's
done.

That is precisely what I was looking for! Thank you very, very much!