How to enable the sa account sql2005

 If you choose "Windows Authentication Mode" during installation, the sa login is disabled. If you later change the authentication mode to "SQL Server and Windows Authentication mode", the sa login remains disabled. To enable the sa login, use the ALTER LOGIN command.  
  sa login can only use SQL authentication to connect to the server.  
   
  In SQL Server Management Studio Object Explorer, right-click the server, and then click "Properties."  
  Under the "Security" page "Server Authentication", select the new server authentication mode, then click "OK."  
  In SQL Server Management Studio dialog box, click "OK" to confirm the need to restart SQL Server.  
  In Object Explorer, right-click your server, and then click "Restart." If running SQL Server Agent, you must restart it.  
   
  Do the following statements to enable the sa password and assign a password.  
  SA the LOGIN the ENABLE the ALTER;  
  the GO  
  the ALTER SA the LOGIN the WITH PASSWORD = '<password>';  
  the GO