Fatal Error during installation of iTunes and can't uninstall it

Ever since I updated itunes to version 9, I can't acces it. I click on the icon on my desktop and a message comes up saying "Please wait while Windows configures iunes" and then a message comes up saying "Fatal Error during installation".

I then try to delete iTunes in my control panel to reinstall it and I can't because this message comes up: "The installer has insufficient privileges to modify this file: C:\Program Files\iTunes\Acknowledgements.rtf"