How to fix an error "change password failed for login sa"?

Sometimes you receive following error while trying to reset MS SQL sa password via SQL Management Studio using Windows Authentication. Follow below steps to resolve it.

Error Message While Resetting SA Password

Login to your Windows VPS via RDP (Remote Desktop Access). This tutorial will guide you to connect to Windows VPS server using the RDP from different operating systems.
Click on Start and go to SQL Server Configuration Manager.
Right click on the SQL Server and select Properties. In the Properties window, select Startup Parameters tab.
In Specify a startup parameter field, type -m; (including semicolon), and click on Add button.
Click on Apply button, and you will be asked to restart MS SQL service, Click OK to close the popup window and click on OK to close the properties tab.
Right click on SQL server, and restart the MS SQL service.
Now, open Command Prompt and run the below query assuming your SQL Server instance name is SQLEXPRESS. Note that, we've reset the password to "AccuWebHosting" for this example, but you'll have to replace your choice of password in @new argument.

osql -E -S .\SQLEXPRESS
exec sp_password @new='AccuWebHosting', @loginame='sa'
go
alter login sa enable
go
exit
Again go to SQL Server Configuration Manager. Right click on MS SQL server and select Properties. In the Properties window, select tab Startup Parameters. From the startup Parameter list, select -m; from the list and click on Remove button.
Click on Apply button, you will be asked to restart MS SQL service, Click OK to close the popup window and click on OK to close the properties tab.
We need to restart the MS SQL service again. Follow step #6 to restart the MS SQL service. Now you can login to SQL Server Management Studio using the new password AccuWebHosting.