I had to hunt around today to figure out how to change SQL Server 2005 authentication mode , so I figured I would document it here in case it slips my mind again.
1. Launch SQL Server Management Studio Express ( Start > Programs > Microsoft SQL Server 2005 > SQL Server Management Studio)
2. Right-click the Server name, select Properties > Security (see picture below)
3. Under Server Authentication, select SQL Server and Windows Authentication Mode
4. Stopped and re-started the SQL Server