There were various kind of protections. One of my games, Inner Space for Windows 3.x, has an install floppy. When you install it, the game sets a bit on the floppy depending on the c:\ drive serial or so and on the installed exe as well. When you want to install it on another computer you need to uninstall it first so the floppy bit is in the default state. Screws you royally when you formatted the c:\ drive... With todays image programs the floppy itself is easily copied. I did try to learn more about what the installer does but never got to far and sadly the game only works with a boot image on Dosbox (the floppy that is, there is also a CD-Rom version that wants to have the CD in drive to play the game - that version only works in plain Dosbox and not in the boot image Dosbox 😀).
Yes, I remember trying to "crack" the game. I bypassed the code protection, but some time later the game stopped to work (it seems that it needed a proper installation, not a "demo" one).
Last year, I bought the game. It was funny to receive a DVD casing with a floppy inside (and before that, they sent me an e-mail with the game). At least, the e-mail game is not protected (I've installed it in my Windows XP and under DOSBox), and I copied the floppy BEFORE installing it... well, in fact, I haven't installed the game from the floppy they sent 😉
I have traveled across the universe and through the years to find Her.
Sometimes going all the way is just a start...
I'm selling some stuff!