[ubuntu] software notification -- no password required to install

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http://ubuntuforums.org – I'm confused. Somewhere I have missed something in upgrading to 12.04. When I click applications > software center and try to install an apt, I can not because I am not root. Use to be it would ask for password. I have to got to a terminal and type 'sudo software-center' to install. When I receive a software update notification and view the list, then click 'install', the changes are installed with out asking for a password. I would like to have a GUI that ask for a password when I want to install something. What do I need to reconfigure? Dave (Hardware)