Another way to delete root owned files is to log into the root account. To do this, open HardDrive -> Applications -> Utilities -> NetInfo Manager. Once you've opened that, go to the menubar and select the "Security" menu. Choose Authenticate to get access to the rest of the menu. Choose "Enable Root User", make a password for the root user, then log out of your account. From he login screen, you'll have to select the box that says "Other..." if you use icons to log in. Then for username enter: root, and for password, whatever password you made. It'll log you in to the computer and you can delete the files you want to, because the root account can manage everything. If you want, you can even disable the root account when you're done.