root.pkg on the MacHD root?

Can you right click it and choose 'Show Package Contents' Then see whats inside..

 

An item located in the "root" of your filesystem is not synonymous with a process running with elevated privileges (root in activity monitor).

Even if you are running as an admin with write privileges to the "root" directory, security sensitive folders within the "root" directory require "System" level privileges to modify.

Secondary click a folder, select "Get Info", and look at the folder's permissions to see the required write privileges for the folder.