Yes, Mike is right - in Vista, Win 7 & Server 2008:
Admin Approval Mode for the Built-in Administrator Account
This security setting determines the behavior of Admin Approval mode for the Built-in Administrator account. With UAC the Administrator account still runs by default with limited privileges and requires a privelege elevation consent to accomplish many administrative tasks.
The options are:
* Enabled: The Built-in Administrator will logon in Admin Approval Mode. By default any operation that requires elevation of privilege will prompt for consent and allow the admin to choose either Permit or Deny.
* Disabled: The Built-in Administrator will logon in XP-compatible mode and run all applications by default with full administrative privilege without requiring consent.
Default: Disabled
SD