IIS Manager could not load type 'Microsoft.Web.Management

I'm using Windows7 with IIS7.5. All the applications were running using the same IIS user, however I had to apply a new user. Now the both users are part of the IIS_IUSRS group. Also, when I open the "Advanced Settings" of my application pool, I can see the correct/new user selected but the problem is that when I try to open any of the sites running under this application pool I get:

HTTP Error 503. The service is unavailable.

When I open the Event Viewer I can see a number of errors related to IIS. However the first three errors are pretty much the same:

IISMANAGER_ERROR_LOADING_PROVIDER_TYPE

IIS Manager could not load type 'Microsoft.Web.Management.DatabaseManager.DBManagerModuleProvider, Microsoft.Web.Management.DatabaseManager, Version=1.0.1.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35' for module provider 'DBManager' that is declared in %windir%\system32\inetsrv\config\administration.config. Verify that the type is correct, and that the assembly that contains the module provider is in the Global Assembly Cache (GAC).

Exception:System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Web.Management.DatabaseManager, Version=1.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

In I've got the same for

Could not load file or assembly 'Microsoft.Web.Management.SEO

and

Could not load file or assembly 'Microsoft.Web.Management.AdvancedLogging.Server

Rightfully, I can't find these dll's neither in GAC nor in inetsrv folder. But also I didn't change anything in order to create the new user. I tried to set the Load User Profile to false but the error remains the same.

Solution 1:

All three modules are external modules that are not part of the IIS installation from disk.

You have a few options:

If you don't use those modules, remove them by editing

%windir%\system32\inetsrv\config\administration.config

as an elevated administrator, find the type names in the file and comment them out or remove them.

Re-install those modules, they should all be available for download from iis.net or you can use the Web Platform installer to install them.

The big question remains: What happened?, I have no idea, adding another user to the configuration shouldn't change anything in the modules.

It seems like the administration.config file came from another server with those modules installed.