Press the Windows key to get into the Metro interface if you are not already there. Enter CMD and right-click on the Command Prompt result that should appear. This opens a list of options at the bottom. Select Run as administrator there. Accept the UAC prompt. Enter the following command to enable the hidden administrator account: net user administrator /active:yes
Once you have enabled the account, you will see it listed in the user accounts control panel applet. Note that the account has not assigned a password to it, and that you should consider setting one to improve account security.