2 - A protected program.
3 - A file that has been changed by the OS so that it cannot be changed or deleted; often very easy to unlock.
4 - A floppy disk which has been physically locked to prevent accidental alteration or to prevent stupid people from modifying the contents.
Dave: i was the same way. i got into it and now I'm "Locked"
Dave: yea once your in the game its hard to get out.