|Since you have to "register", then I'd suspect it is protected. I suspect they eula states how you are allowed to use it and re-use it.|
Might be how you cloned it too. A file by file may have failed where a bit by bit may have or not worked.
There is a lot of information a program could get from a hard drive and some places in the hard drives flash memory that could be read to include into a protection scheme. Not only the drive type and mfg, but dates and sizes and such. You'd be hard pressed to find two exact drives in an ordinary production run. Who knows what else may have been used to protect the program.
I have seen some old ones that were tied to the command.com version. Some that made odd formatting, some that were tied to position in bits from the beginning from the drive. Some that used external hardware keys. Some that used hardware information and the list goes one.
Why did it take me over a year to phone in a problem to ATT?