I used to sell small business apps on floppy drives. For copy protection, one of the best tricks was to physically damage a sector and try to format it.
You take a floppy disk, use a pin to make a hole on the magnetic medium at a random place, then format the disk so that sector is marked as a "bad sector". You hardcode the sector ID in your app, then when your app runs, you try low-level formatting that sector. If it can be formatted, it's a pirate copy.
Floppy disks had physical read-only mode, so my app asked users to put their disks in read-write mode to work :)
You take a floppy disk, use a pin to make a hole on the magnetic medium at a random place, then format the disk so that sector is marked as a "bad sector". You hardcode the sector ID in your app, then when your app runs, you try low-level formatting that sector. If it can be formatted, it's a pirate copy.
Floppy disks had physical read-only mode, so my app asked users to put their disks in read-write mode to work :)