I posted this on another thread yesterday.
There are a couple of ways:
Open a command prompt (Run as Administrator).
Type the following command and enter.
net user administrator /active
Log out and see if you have a new alternative login, as well as your existing one. If not, do it the long way.
Shut down the computer for a cold boot. Tap the "F8" key as you are booting.
Select "Safe Mode with networking" from the boot menu.
Log into windows 7 with your personal account that holds the administrator access.
Open a command window.
At the command prompt type the following net user administrator /active
Log out and log back in as administrator.
Another way
Go to Start
Type Control UserPasswords2.
Click...