How to fix “Windows NT user or group servername\Administrators not found” in MSSQL

Trying to add the local administrators group to a SQL server with sys admin (sa) server roles? Getting the error?below? I have a very simple fix.

Windows NT user or group ‘COMPUTERNAME\Administrators’ not found. Check the name again. (Microsoft SQL Server, Error: 15401)

Instead of adding “COMPUTERNAME\Administrators” change it to “BUILTIN\Administrators” and it will work just find. Just erase your computer/server name and replace with BUILTIN.

This fix should work for SQL Server 2005, 2008, 2012, and 2014.