I appreciate the time and effort you've put into helping poor stupid me, but as I said in my earlier reply to you, I did exactly that. Here's the sequence of events (without screen shots):
1. I opened Quicktime 7, expecting to use Pro, only to find it was no longer the Pro version. No Pro functions were available.
2. I went to the Quicktime 7 menu, clicked on Registration, and entered into the registration window the exact same registration name and code that are in my email from years ago. I then clicked on the Buy button.
3. A browser window opened telling me that quicktimepro.apple.com could not be found, and the message "Invalid registration" or something similar popped up in the Registration window.
4. Thinking this might be a temporary glitch, I repeated the process several times, with the same result each time.
To sum up: Quicktime 7 Pro somehow reverted to the free version. The registration data that I used when I originally purchased Pro no longer works, and Apple tells me they can't recover my registration data. Apple also tells me they can't explain why my previously registered Pro version was suddenly mysteriously unregistered.
Thanks for trying to help, though.