"Interactive" copy protection
I had a Commodore 64. There was a computer store that would rent games for 3 days at a time (and if we rented on a Thursday night, we had an extra day to bring it back!) We would rent a game that had some type of code wheel or code book. For the youngin's here, in order to play the game, at some point in the loading process, you needed to type a code found only by matching up symbols or finding the right passage in a book before you could continue, otherwise the game didn't load (Look to "Pool of Radiance" or "Bards Tale" or "Zak McCracken").
The best part of renting the game was copying the program and then spending the rest of the weekend trying to copy the wheel (only time we ever really used paper plates) or finding a way to copy a huge sheet of black text on dark brown paper to get the codes.
