As others have said, it will unregister the card from the program it's in and register it to the new program. I don't know if it matters if both accounts are in the same name or not as to if it unregisters it or just gives a the card is already registered error message. I believe the only time that will not happen is if the card you are registering is the only card left on a program, then it will not move it (nor will it let you register it to the new program). I don't think, but may be wrong, it won't let you remove all the cards from a program by transferring them out.