If you select Windows Authentication mode during the installation process, the SA login is disabled. If you later change the authentication mode to SQL Server and Windows authentication mode, the sa login is still disabled.
To enable the sa login, use the ALTER login command.
The sa login can only connect to the server using SQL authentication.
Workaround:
1. First select Server (right-click), Properties---Security server Authentication modified to "SQL Server and Windows Authentication mode"
2, followed by the "security" on the server, login name, check the sa login account (right-click)-----Login modify to enable
3. Execute the following statement to enable the SA password and assign a password.
ALTER LOGIN sa ENABLE; GO ALTER with = ' 123456 ' ; GO
Original Sticker Address: http://www.cnblogs.com/jasmine_xm/archive/2010/03/21/1690782.html
SQL2005 sa user is disabled by workaround