Rob has an old MacBook Pro and he wants to move a program from it to his newer Mac Air, but he needs the serial number. The program in question is called inSSIDer. Leo says that when you register a program, it stores the product key in a folder on your Mac, and then when you log in, that file is verified. Leo also says you can try logging onto the Megageek website, who made the program, and see if you can find your serial number there. If so, it's a simple matter of just reinstalling it with the serial number. But if that doesn't work, then download the personal version. It's free.