Turn off UAC
Ran into the same problem on several occasions. The problem here is one of language, they tell you that you are logged in as administrator but you really don't have full administrative privileges thanks to User Access Control. You can got to Control Panel/Users and click on Change User Account control settings. then pull the slider down to "Never Notify." You will get a warning message but you can ignore it. Now close everything and make the changes you were trying to make to the system.
I would recommend that after you have made all the changes you need to make that you go back and move the slider back to its original default position so that you security is not compromised.