IIS Fails with error “App-Domain could not be created”

Getting the error “Failed to execute request because the App-Domain could not be created.” can be fixed by doing the following to “re” register ASP with IIS.

Other descriptions of this error can be

Error: 0×80131902
Failed to initialize the AppDomain:/LM/W3SVC/1/ROOT
Exception: System.Configuration.ConfigurationErrorsException

SOLUTION:
--> adding the IIS_WPG read/write access also worked for me, but either make sure that all the subfolders inheret their parent dir permisions settings or apply the permissions to EVERYTHING inetpub and below. I went to IIS and right clicked on my website, clicked permissions, then added IIS_WPG from the local server (we also have a IIS_WPG domain group). I only left the read box checked and it solved the problem. still if not then follow below steps

-->First Stop Web Services by typing the following at the command prompt:
net stop w3svc

Uninstall all instances of ASP.NET by running the following command:
aspnet_regiis.exe -ua

You are now ready to re-install ASP.NET to IIS with the following:

aspnet_regiis.exe -i

Lastly you need to start up the webserver:

net start w3svc