It may sound strange to people who were born later. But in 90s these mechanisms were in infancy. It was normal for computers to auto-login and have no password at all, processes could each read entire memory on the machine. Software was cracked the moment it came out and it was assumed people bought any software because they feared legal action rather than because they had no other way to get their hands on it -- lat…
One mechanism which was sometimes used for more expensive software was a dongle connected to the parallel port.
Enough to keep honest people honest and not copy the software to their immediate friends, but if the software had people interested in pirating it someone would disassemble it and just jump over the part that looked for the dongle while keeping all the software functionality intact and these patched versions would be readily available online to anyone who knew where to look.
At the end of the day not really any more secure than various software-based copy protection schemes, just more wasteful due to the extra hardware.