See how to reset SQL Server SA password to unlock SA account when SQL Server forgot/lost SA password and failed to login with Windows Authentication.

1. Reset SQL Server SA Password without Login
As we all know, the SA user is the super administrator account in SQL
Server. Once forgot / lost SA password and cannot connect to SQL Server
instance, what to do? Can we find some ways to reset or recover SA
password and unlock the SA account? Especially when the Windows
Authentication mode was also disabled so you are totally locked out of
your SA account, is there one way to reset SQL Server SA password?
Should it be the only option for us to reinstall SQL Server? Is there any
easy way to allow us to instantly reset SA password without login to SQL
Server? Of course there is.
SQL Server lost SA password with Windows Authentication disabled?
Following, see how to reset/change SA password without login to SQL
Server.
Step 1: Stop SQL Server services. (Open SQL Server Configuration
Manager and stop all services.)
Important: This is the key step you should do firstly before you reset SQL
Server SA password.
Step 2: Install SQL Password Geeker on your PC.
SQL Password Geeker is a tiny and easy-to-use SQL password recovery
tool, with which you can reset SA user or other users passwords for MS
SQL Server 2005/2008/2012/2014.

2. Step 3: Open SQL Password Geeker and import master.mdf file.
1. Run SQL Password Geeker.
2. Click on Open File button.
3. Navigate to the disk where your SQL Server is installed. Go to
Program FilesMicrosoft SQL
ServerMSSQL.1MSSQLDatamaster.mdf.

3. 4. Select the master.mdf file and click Open button.
5. Then you can see the master.mdf file is imported in SQL Password
Geeker.

4. Step 4: Reset SA user password
After importing the master.mdf file, you can see all users in your SQL
Server are displayed on the software window. So you can select the SA
user or any one user displayed and reset its password.
1. Select the SA user and click on Reset button.
2. Type a new password for the SA user in the “Reset Password” dialog.
Then click OK to save changes.

5. 3. A dialog saying password successfully changed pops up to tell you
have successfully reset SA password. Click OK to close the dialog.

6. You can see that, before resetting SA password, the SA password is
labeled “Unknown”. When SA password has been reset, you can see the
new SA password displayed on the window. Remember it then close SQL
Password Geeker.
Step 5: Start SQL Server services
When SA password has been successfully reset, you must do not forget
to start SQL Server services. Make sure all services are running and you
can login to SQL Server with the new SA password.
So, next time you forget SQL Server SA password or other users
passwords, just use SQL Password Geeker to reset SQL Server password.
Related:
How to Reset SA Password on SQL Server 2005/2008/2012/2014