Are you talking about copying files off your drive or initializing it? If you are giving your computer to someone else it is a good idea to initialize and reinstall the OS. You can wipe and overwrite your drive's sectors if you want to be extra careful.
Boot up from the install DVD and you will be able to initialize the hard drive.
This is the kind of thing that makes me technically a liar when I tell people, "Don't worry, there's no way to 'accidentally' screw up your computer. Just use it."
This is the kind of thing that makes me technically a liar when I tell people, "Don't worry, there's no way to 'accidentally' screw up your computer. Just use it."