4. Explosionware
Explosionware did damage to your system if your software was illegitimate. The in-program literature warned of dire consequences if you tried to tinker with it.
I only ever saw this in software that existed in a legal gray area like emulators and decompilers. The first time I saw this in the gaming world was with a Game Boy Advance emulator called NO$GBA (or No Cash GBA).
Taking someone else's work and trying to pass it off as your own, through text and graphic changes, was a common a practice in the world of emulation. NO$GBA threatened dire consequences for your system if you tried to run a modified copy.
5. Disc in drive
Most games in the CD era required that your disc be left in the drive even after you put your activation key in. And CD drives used to be loud, so this meant you had a jet engine drowning out the game music.
This was among the least effective because a no-CD crack was usually out before the games reached retail. As always, honest users who didn't know about or were unwilling to use cracks were made to suffer.
Some games were a little more lenient, and would still let you play the game without some of the game's content like videos, audio, or levels if you didn't have the CD.
6. Code wheels
Code wheels are something I've only heard of in legend. A game with a code wheel would direct you to turn the wheel in a certain way to reveal the code needed to launch the game. These were harder to copy than something like a manual or map due to the complexity. An aspiring copier had to disassemble it, copy each component, and provide instructions for assembly.
7. Demoware
Some game developers were under no illusion that pirates were the only people running illegal copies of their games. Instead of using goofy, easy to bypass protections, they simply turned the game into an extended demo.
You could play to a certain point or for a certain amount of time without passing the copy protection check, but that was it.
8. Details in the disk
These had a similar protection scheme to one-time use disks, but used bits hidden in the disk to foil attempts at copying it. Changes to the disk's boot sector were used to mark the disk as legitimate. The software knew to look for these, and they wouldn't be there in a copy unless the copying software knew to look for the changes.
9. Good old-fashioned sloganeering: "Don't copy that floppy"
It was a dark, awkward time in the world of software. Despite M.E. Hart's dire warnings, copying software has yet to kill the software industry.
Michael Robinson writes about games, movies, TV, and other forms of entertainment at his blog and on Twitter at @mkronline.
