Set to allow SQL Server login
1. log in with the window method, select the database instance, right-click and select Properties-security: Change the server authentication option from "window Authentication Mode" to "sqlserver and window Authentication mode ". Click OK to close the current object Resource Manager.
2. Log On again using window verification. In the tree structure on the left, select the "Security" option under "Database"-login name-Sa, right-click Properties -- enter the SA password you want to set in "sqlserver authentication", click status, and select Grant and enable.
3. Restart the sqlserver service. Remember, it is to restart the service, not to disable sqlserver2005 and then enable it.
If you do not restart the sqlserver service and log in directly with SA, the following error is reported: "User 'sa 'Logon Failed. This user is not associated with a trusted SQL server connection ".
How to restart sqlserver service: go to window service, find "SQL Server (MSSQLServer)", and select restart. Alternatively, enter: net stop MSSQLServer at run time, And then: Net start MSSQLServer.