Activate and use the hidden Administrator account to carry out what you need to do
Start Menu > Programs> Windows System> right click Command Prompt > select Run as Aministartor.
net user administrator /active:yes
reboot and the Adminstartor account will be shown
boot into that and do what you require to windows.
on completion to deactivate the account
go to command prompt again and type
net user administrator /active:no
reboot and the Administrator account will not be shown.