I don't have the email from 9 years ago - but I do have the registration code. QuickTime (System Preferences) is not accepting it (Invalid registration), and my name is the same as would have been in the email (tried every variation I can think of). Apple support webpages says my Serial Number (in System Profiler) is too far back in history (nine years, but their hardware still lives).
From nine years ago it could be a key for either QT 6 or QT 7, as Kirk indicated. A QT 6 key will not work for QT 7.
If you're sure you purchased a key for QuickTime 7, then you would need to make sure you're entering in both the user name and key code exactly as in the email Apple sent you. Any error in either, including leaving off a salutation (for instance, if the email says "Mr. John Smith") will cause the registration to error. If you no longer have that email, then you can only guess as to how they phrased your name.
If you can't get it to work, you'll need to purchase a new key. Apple keeps records for orders only back 18 months.
Thanks - that was the nudge to making it work. I did have the correct Quicktime key, but didn't prefix my name with a 'salutation', probably one of the dropdowns in a mandatory field used at registration. Hey presto, my nine year old box of tricks, "obsolete" according to the boys & girls at the Leeds Apple shop, adds one thing more to its pre-crash repertoire.
Unfortunately, the trick I was hoping my originally paid-for application would perform, that is converting .wmv to .mp4 video format for Quicktime playback, remains as intractable as before without using a tool external to Quicktime. QT 7 pro *can* run media files not in one of its recognised formats, but the original file has to be exported from source (.wmv) to alternative (mpeg-4) forms first - and QT 7.6.4, pro or otherwise, doesn't recognise .wmv as a importable "movie" format in the first place! Doh !
I've already been doing the conversion process in up to half-gigabyte sized batches (they run overnight) with an excellent, and properly backwards compatible, video converter application called Prism (from NCH), but it's not shareware and the trial version expires in "a few days". Continuing to use Prism is not going to be a huge cost, but it would be preferable if Quicktime DID what it *still* says on the tin, that is (from http://www.apple.com/uk/quicktime/extending/):
"QuickTime 7 Pro can convert your media to different formats, so you can watch a movie or video on your iPhone, iPod and Apple TV."
Not .wmv movies it doesn't !
QuickTime Player has never been able to even open Windows media formats without third party software help. It can't convert what it can't open and the third party software help (Flip4Mac) requires you to upgrade from their free version to export.
Spend some money.
Yes, but ...
Prism lets me get on with other things while it's doing its job (converting batches of .wmv to mp4 files, here). It's backwards compatible (with OSX 10.4.11 in my case) and runs without memory or processor hogging. It's about 10 dollars more than Flip4Mac pro but (guess what) Flip player is not backwards compatible. I don't have to search the back pages of the internet for possibly illegal downloads which might do some damage and won't be as good as Prism. I remember using Flip4Mac for occasional one-off conversion jobs - I'm doing up to 20 50-100Mb video files at a time. Not worth it for 10 dollars more.
If you haven't tried Prism video file converter, I recommend it (and that's not something I do very often).