Click start, go to control Panel and select "user Accounts".
Seeing the window control your account, click "Manage another account".
Select the account you want to grant administrative privileges.
Click on "Change account type" and then select "Administrator". To confirm the changes.
In the same way, change the type of the account from which you want to take away the admin rights.
Restart the computer (or reconnect to the system).
With the account named "Administrator" doesn't work.