After my success at home, with the installer, I decided to try it at work, so I could fiddle with DNN when I have some spare time.  But this time, I was not as fortunate:

Here is what happened:

I installed using just the defaults (sqlserver express, DotNetNuke directory, no qualifier on DB table names)

But when the program went to localhost/dotnetnuke to do the install it brought up a web page saying:
 
A name was started with an invalid character. Error processing resource 'http://localhost/DotNetNuke'. Line 1, Position 2

<%@ Page Language="vb" AutoEventWireup="false" Explicit="True" Inherits="DotNetNuke.Framework.DefaultPage" CodeFile="Defa...

So I opened the sln in visual studio,
it said that the site wasnt set to framework 2
so applied framework 2 (and now the directory says its framework 2 in IIS)

So then I tried to go to localhost/dotnetnuke and a 403 (page cannot be shown).

So I went to the directory, and under the security tab I assigned NETWORK SERVICE (which hadnt been there before), but I still got the same thing (403, page cannot be displayed).

I uninstalled DNN from the PC and started again.

Got a message that the directory already existed, but I let it use the same directory (DotNetNuke).  I got a message that the database still existed, so I used a different one (DNN).  This time, to be safe (sinse a dotnetnuke db already existed on the server) I added an object qualifier (dnn1) for the db names. 

... but I got the exact same error page.

You have bitten off a very big challenge with this project.  I dont envy you.  There is a reason that nobody has ever created an install program before and sold it, even though the profit involved could have been considerable. They would have spent way too much time giving their money back :-) And Im sure you dont have a bank of  computers running every concievable configuration like the guys at Microsoft.

You are doing a great service, and I only wish I had the expertise to assist you further.

Ray