SQL Server stores the password as a hash in the master.mdf file. With SQL Server Password Changer you can quickly reset a lost SA password, instead of recovering the original password. However, the master.mdf file is inaccessible while SQL Server is running. SQL Server service needs to be shutdown before resetting the password offline.
Step 1: Stop SQL Server Service
In SQL Server Configuration Manager, expand Services, and then click SQL Server.
In the results pane, right-click the instance of SQL Server, and then click Stop.
Click OK. A red box on the icon next to the server name and on the toolbar indicates that the server stopped successfully.
Step 2: Reset SA Password
Click on the "Open File" button. The program will prompt you to choose the master.mdf file for your SQL Server instance. By default, the master.mdf file is located in the directory C:\Program Files\Microsoft SQL Server\MSSQL\Data. If you don't know the folder location, you can use the Windows Explorer search bar and enter the file name master.mdf and search through your system partition.
Once you've chosen the master.mdf file, the program will decrypt it and then show you a list of database user accounts. Select your SA account and click on "Change Password" button. Set a new password and click OK.
Now you've successfully reset a lost SA password. Go to the SQL Server Configuration Manager and start you SQL Server service again. You can then login to your SA account with your new password.