Hi and thanks for the answer!
Anyway I couldn't solve my problem. I've checked all my permission on the folders and they seems to be ok. I noticed that the error is that it cannot open the preferred database. It says access failed and then Access failed for user NT AUTHORITY\NETWORK SERVICE.
Sorry If I explain this way but my .NET framework is in Italian. Anyway this is what it returns:
"DotNetNuke.Services.Exceptions.ModuleLoadException: Impossibile aprire il database utente predefinito. Accesso non riuscito. Accesso non riuscito per l'utente 'NT AUTHORITY\SERVIZIO DI RETE'. ---> System.Data.SqlClient.SqlException: Impossibile aprire il database utente predefinito."
Translated should be something like this:
"DotNetNuke.Services.Exceptions.ModuleLoadException: Cannot open the preferred user database. Access failed. Access failed for user 'NT AUTHORITY\NETWORK SERVICE'. ---> System.Data.SqlClient.SqlException: Cannot open the preferred user database."
Please help!!!!