>>If you want to be prompted for login, remove User Id and Password from the connection string. The SQL Server has to be configure for Mixed mode authentication.
>>

>>Connection1=Data Source=MyServer;Initial Catalog=MyDatabase;
>>

>
>I had to disable the Windows Authentication.

I believe this is a wrong decision. When you install your SQL Server, you need to specify mixed connection. Make sure to create a complex password for sa (default) account.