On Mon, 22 Sep 2014 12:44:33 +0100, Joe User wrote:

Is it not disabled by default?

No, it's not, it's temporarily inactive.

On a machine with a single standard user account visible on the
login screen, password protected or not, all you need to do is
boot in safe mode and select command prompt(admin) from the
relevant context menu.

A dialog pops up asking for a password, leave it blank, there
isn't one, and bingo, you're an admin.

Make the hidden Administrator account active with net user
Administrator /active:yes and sign out.

So, yes, it's disabled by default.