How To Add Back The BUILTIN Administrators Group In SQL Server

How To Add Back The BUILTIN Administrators Group In SQL Server

While disabling if you had dropped the Built-in Administrator account from the SQL server. Please follow the steps to add back The [BUILTIN\Administrators] group back.

First try in Test box, before doing any changes in Production box. 
USE Master

Go

EXEC SP_Grantlogin 'BUILTIN\Administrators'

GO

EXEC SP_Defaultdb 'BUILTIN\Administrators', 'master'

GO

EXEC SP_Defaultlanguage 'BUILTIN\Administrators', 'us_english'

GO

EXEC SP_Addsrvrolemember 'BUILTIN\Administrators', 'sysadmin'

GO 

The other way as well you can add like below. 

USE Master

GO

CREATE LOGIN [BUILTIN\Administrators] 

FROM WINDOWS

WITH DEFAULT_DATABASE=[master],

DEFAULT_LANGUAGE=[us_english]

GO