Kev,
There are a couple of reasons perhaps for the error, let me explain.
First of all be sure that RSLinx is NOT running at all, either as an application or as a service. The EVMOVE/MASTER DISK routine may actually have 2 different programs, one that is based on 16 bit and the other is based on 32 bit. You may try the other utility. The serial numbers on the activation file must match the serial number on the "Master" disk, if they don't you will encounter a problem. If the "Master" has it's write protect window set for protection, that could be a problem. Also, there is a problem with USB floppy drives and the XP system, there is a patch available. I had problems moving activations until I found the patch. I don't remember the patch number but I'm pretty sure I got it from MS.
Lastly be sure to have administrator rights, you may need to log onto the computer with admin rights.
Good Luck!
Bitmore