seems you have windows vista or above os version even you are the admin you will not have full control until you disable UAC (user access control)
or you have to enable built in administrator
click start run > type > "net user administrator /active:Yes" to activate built in admin and you have to start using that account
"net user administrator /active:no" for deactivate. suggestion : you do not have to do that microsoft created this option only to protect your systemits up to you now.....