In Windows 7 there are a couple of differences between the local Administrator account and any new user accounts you create on the system that belong to the Administrators local group which you should be aware of. Specifically:
The default Administrator account has a well-known SID
By default UAC does not apply to the default Administrator account (unless specified by Group Policy).
On home SKUs of Windows 7, by default the default Administrator account has no password and cannot authenticate over the network. In addition, by starting the system in Safe Mode the user can log in with no password for recovery and troubleshooting purposes.
Mitch Tulloch is a seven-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.