Setup is set to allow startup from another device. If the Boot First Device option is not set to allow the computer to start from another device, the computer returns to the operating state it was in when you turned it on.
If the hard drive password, the external hard drive password, and the system password are the same, the computer prompts you only for the system password. If the hard drive password is different from the system password, the computer prompts you for both. Two different passwords provide greater security.
NOTE: The administrator password provides access to the computer, but it does not provide access to a hard drive that is protected by a hard drive password.