Thanks for you responses.
In SQL Server Enterprise Manager,
Users: existing-> dbo (Login name sa), guest(no Login name)
I added user account -> machinename\ASPNET. But Login Name is not shown.
In Permissions: SELECT, INSERT, UPDATE, etc, all.
In Database role membership: public, db_owner, db_accessadmin, etc, all.
I also added a user account ASPNET (Login name is shown as ASPNET). Gave full access.
But still : Login failed for user 'MACHINENAME\ASPNET'.
In fact I just run examples from Microsoft and the database pubs is there in SQL Server.
Have a nice weekend!