This error is really starting to bug me. I started to get the error a week ago where I started to receive "The requested page cannot be accessed because the related configuration data for the page is invalid." errors.

Here is what I have done so far.

1. Fresh Installation of Windows 7 Ultimate 32 bit.

2. I have two directories for web applications (c:\webapplications and c:\webDNNapplications). The security on the directories is set to allow NetworkServices Full Control.

3. In IIS, C:\webapplications is set for the location for the web site. I added Dev as a web application and pointed it to c:\webDNNApplications\LocalDNN512.

4. I changed the permissions on the ApplicationPools to be NetworkService vice default ApplicationPoolIdentity.

5. I downloaded a copy of DNN 5.1.2 Install file and moved contents to c:\webDNNApplications\LocalDNN512

6. When I attempt to load DNN (http://localhost/dev) I receive the following error information.

HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid.

Detailed Error Information
Module IIS    Web Core
Notification    BeginRequest
Handler    Not yet determined
Error Code    0x800700b7

- Config Error Cannot add duplicate collection entry of type 'add' with unique key attribute 'name' set to 'ScriptModule' 
- Config File \\?\C:\WebDNNApplications\LocalDNN512\web.config
- Requested URL http://192.168.11.110:80/dev
- Physical Path C:\WebDNNApplications\LocalDNN512
- Logon Method Not yet determined
- Logon User Not yet determined

Config Source
58:     <modules>
59:       <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" preCondition="managedHandler" />
60:       <add name="Compression" type="DotNetNuke.HttpModules.Compression.CompressionModule, DotNetNuke.HttpModules" preCondition="managedHandler" />
 

This error is a real pain and I have the feeling that it is something really simple that I am overlooking. Of course, I have lost some serious time.

Any help or insight will be greatly appreciated and a great incentive for a good nights sleep.

Thanks

Ray

Actually, I think that I figured it out and the solution was to change permissions to use the IIS AppPool\DefaultAppPool and a small change to web.config.

In a nutshell;

1. Changed Application Pool back to ApplicationPoolIdentity
2. Added IIS AppPool\DefaultAppPool to the directory and Web Site permissions.
 Read http://learn.iis.net/page.aspx/624/application-pool-identities/ for directions to change directory permissions.
 To change the web server permissions,
 -> in the IIS Manager, click on the main Web Site
 -> in the right column, click on Edit Permissions.
 -> Use the same process for changing the permissions as you did for the directory
3. Added the following line to the web.config under <system.webserver><modules>
 <remove name="ScriptModule" />
4. At this point if you attempt to install DNN, you might get an error message regarding incorrect casting of the ScriptModule. This issue is caused when the root web has references to .NET Framework 3.5 as when a website exists at http://localhost that uses Framework 3.5. I removed the files from my root web and DNN installed normally.

Based on what I read, IIS 7.5 is configured to use IIS AppPool\DefaultAppPool which offers additional security instead of using NetworkService. The referenced article makes note of the setting. There are a number of articles that explain how this permission set functions.

Regarding removing the root web.config file if it referenced .NET Framework 3.5, I found a this reference on the DotNetNuke Forums.

I was able to complete an installation of DNN and it is up and running. Now I can rest comfortably.

Thanks

Ray