After a Typical installation of Microsoft SQL Server 2000 or of Microsoft SQL Server 2005, Windows Authentication is the default security mode. Therefore, after you install SQL Server 2000 and you attempt to connect to the SQL Server server by using a standard login like system administrator (SA), you may receive the following error message:

SQL Server 2000 has three types of installations:

•	Typical
•	Minimum
•	Custom

For more information about these installation types, refer to the "Setup Type: Typical, Minimum, or Custom" topic in Microsoft SQL Server Books Online.

After you set up a SQL Server 2000 server by using the Setup Wizard to perform a Typical installation or by using the Sqlins.iss file for a typical unattended installation, the default security authentication mode is Microsoft Windows NT Authentication, which is different from Microsoft SQL Server 7.0. In SQL Server 7.0 the default authentication mode is Mixed (Windows NT Authentication Mode and SQL Server Authentication).

You cannot use a SQL Server Standard security login account after a Typical installation of SQL Server 2000 until you change the authentication mode to Mixed.

To change the authentication mode from Windows NT Authentication Mode (only) to Mixed Mode, use the following steps:

1.	Open the Enterprise Manager.
2.	Expand a Server group.
3.	Right-click a server name, and then click Properties.
4.	Click the Security tab.
5.	Under Authentication, click the SQL Server and Windows option button.
6.	Restart SQL Server in order for the change to take effect.

Note If you are using SQL Server 2005, see the "How to change server authentication mode" topic in SQL Server 2005 Books Online.