Information
Uses Windows Authentication to validate attempted connections.
Windows provides a more robust authentication mechanism than SQL Server authentication.
Solution
Perform either the GUI or T-SQL method shown:
GUI Method
 - Open SQL Server Management Studio
 - Open the Object Explorer tab and connect to the target SQL Server instance.
 - Right click the instance name and select Properties
 - Select the Security page from the left menu.
 - Set the Server authentication setting to Windows Authentication Mode
T-SQL Method
Run the following T-SQL in a Query Window:
USE [master]
GO
EXEC xp_instance_regwrite N'HKEY_LOCAL_MACHINE', N'Software\\Microsoft\\MSSQLServer\\MSSQLServer', N'LoginMode', REG_DWORD, 1
GO
Restart the SQL Server service for the change to take effect.
Impact:
Changing the login mode configuration requires a restart of the service.