I just tried to re-install and register MC14. I used the product code printed on the CDROM, and it installed just fine. But when I tried to register it, I got an error message saying "invalid product code" (or words to that effect). I'm pretty sure that the register software knows what my product code is because I didn't have to enter it; it popped up as the default code when the page opened. And I've checked this code against the one on the CDROM; it's identical.
What's going on? Here's a possible clue: I once had another copy of MC14. Perhaps the web site is expecting the code from that one??