Upgrading to iTunes9 on Windows Vista won't install

It says we do not have permissions. We uninstalled and tried to reinstall, and keep getting errors that we don't have permissions for Quicktime folders. I tried to delete the Quicktime folder, but it says I don't have permissions for the folders, chiefly the Quicktime\QTSystems folder. I checked the permissions and it won't show or let me change owners. We're using the administrator account.