Thanks Sebastian!
I found the code and indeed, there are differences, though I don't know if the end brackets and anything in between will display...

Which should take precedence: the code string in "appSettings" or should what's in "connectionSprings" be duplicated?

I'll follow up to see if the code I pasted dipslayed properly...

Bill,
Thanks for deleting that info you unscrambled AND the advice for fixing the code.

I'm fortunate that I discovered I had MS Visual Studio 2005 Tools for Applications that let me look at the web.config file in color coded text. That help me discover what you were saying about the commented-out SQL 2005-2008 definers in the {connectionString}{/connectionString} XML tags. That help the light bulb go off when I saw the line {add name="SiteSqlServer"...} and discovered the ' --> ' comment tag was to the left of {add key="SiteSqlServer"...} inside the {appSettings}{/appSettings} XML tags below. I cut and paste that ' -->' comment tag to the right of the Application Setting Key for the Site SQL Server then save.
After updating web.config offline as you stated [control-S works for XML files too, I presume] can I drag this corrected to file to overwrite/replace current web.config file [after I make a backup, if the corrected file don't work..] and see if that lets my downloaded Modules install on my website? Have I interpretted that correctly? After replacing web.config, should I log in as Host and Restart Application in Site Setings before I try installing a DNN Module?

Thanks!
Glenn