I am trying to connect to SQL Server 2008 using 'sa' username and its password. In the SQL Server log file I see this error:
Login failed for user 'sa'. Reason: An attempt to login using SQL authentication failed. Server is configured for Windows authentication only.
When I right-clicked on the server -> Properties -> Security "SQL Server and Windows authentication mode" is chosen.
I thought it's a problem with the 'sa' user so I did:
ALTER LOGIN sa ENABLE ;
GO
ALTER LOGIN sa WITH PASSWORD = '<enterStrongPasswordHere>' ;
GO
But it didn't help.
What else can it be?
It looks like you will need to restart your SQL Server according to the MSDN link on enabling Mixed-Mode Authentication
There is another article (user comment at the bottom) referencing a registry key that you can look at; it also says you will need to restart the service once you have changed it.
From the first link:
To change security authentication mode:
In SQL Server Management Studio Object Explorer, right-click the server, and then click Properties.
On the Security page, under Server authentication, select the new server authentication mode, and then click OK.
In the SQL Server Management Studio dialog box, click OK to acknowledge the requirement to restart SQL Server.
To restart SQL Server from SQL Server Management Studio