I just tried to add the <domain>\Domain Users group as a SQL Server Login. (I took a crack at <domain>\Everyone as well. No luck with that group either.) The instance of SQL Server lives on the office domain controller. I was able to accomplish what I needed by adding BUILTIN\Users as a SQL Server Login. (BUILTIN\Users contains <doman>\Domain Users.) But the question still remains, why didn't <domain>\Domain Users or <domain>\Everyone work? Does the restriction stem from SQL Server Express? The fact that instance of SQL Server resides on the domain controller? Something else?