For those that are wondering you can unlock the acccount that vista itself uses to make changes to your computer. just to let you know this user doesn't have the annoying UAC and also if you make changes to System32 for example you won't get a pop up showing confirmation etc...
First of all open Command Prompt With administrator capabilities and type in:
[Net user administrator /active:yes]
and when you log off the user will be there it is I also advise you to put a password on that user.
If you want to deactivate the user then in an account that isn't the one you unlocked type in command prompt with administrator capabilities:
[Net user administrator /active:no]
Hope this helps