This security setting determines which users can take ownership of any securable object in the system, including Active Directory objects, files and folders, printers, registry keys, processes, and threads.
Assigning this user right can be a security risk. Since owners of objects have full control of them, only assign this user right to trusted users.
Computer Configuration\Windows Settings\Local Policies\User Rights Assignment
At least Windows XP SP2, Windows Server 2003
User Rights security settings are not registry keys