Learn what connectivity is being used, and then change the default user to another SQL Server login or use Windows security.
Check under Database->Set Location.
If it's using ODBC, you can change the ODBC settings to use Windows Authentication which just passes the user login on to the database, or use another SQL Server defined user.
Databases require a login, so you'll have to change the login to some other user, or use a trusted connection (Windows authentication).
-k