[a-dub]

i think your leg was being pulled.

that said, one of the first copy protection schemes involved writing specific sectors to a magnetic disk with an invalid checksum. when the program would start, it would verify that reading those sectors would return an error, but if you used a regular disk copy program it would not copy the invalid sectors- either resulting in an aborted copy or a copy that would zero out the bad sectors on the target which would not produce the expected read errors on startup telling the program it had been copied.