One thing that can work, rather than take ownership, is to specifically give your username the permissions you need on the actual files you need to edit/control.

You will need to unhide the hidden administrator and log in as that user, then you need to right click on the files you wish to edit, select the security tab and ass the required action to your user name, Full control is normally the one to use.

As Shawn has stated, the system will eventually reset the Owner, but it does not always remove new rights held by a user