Microsoft says my 10-year-old Windows 7 CD Key is not valid  

macnab said:

Thanks, everyone.

Booted up this morning and my PC says it is activated thanks to a digital licence linked to my Microsoft account.

It also says that the last product key I entered cannot be used with this PC.

Don't ask me how this works, but it does. (It did keep telling me try again later.)

Once activated at MS server it should always stay activated but some times server is slow to respond immediately. You can also go to your MS account with your MS credentials and delete past accounts/installations. I have MS account thru hotmail.com, changed systems and motherboards at least 4 times and reinstalled W10 several times also, never a problem with license except some late (couple of hours) responses from server when it said it wasn't activated. Also upgraded from W7 Ultimate Retail tp W10 Pro but it was very early when W10 just started. Same with another license on same machine but that one is now running Insider Developer version.

macnab said:

Makes sense. That is why it said try again later.
Still strange that the key is invalid.

I entered W7 key only once (and that was at the time of upgrade) for either instance, always with my hotmail account and credentials and never had to do it again even after clean installs and MB changes. I even use my W10 cellphone (Lumia 630 Dual) with same account. Only other thing I do is to go to my account and delete obsolete devices. I must have this same account for 30+ years, just change passwords every now and then.
BTW, you can contact MS for problems like that using Skype in textual mode.
Here in Belgrade we have regional MS office so I could go there and knock on the door if they pi$$ me off too much. Actually, one of W7 licenses was given to me by that same office "for services rendered" a while ago. First one was discounted upgrade from Vista.

macnab said:

Makes sense. That is why it said try again later.
Still strange that the key is invalid.

Your story has huge holes - you need to post screenshots next time. If the Activation server says wait - then just wait.
Why anticipate going through the whole palava to send your stuff to MS just 'cause they said it's fake? MS support has never been known to be the brightest crayons anyways.

macnab said:

I went through the palaver because it said Wait for 2 days running.
It also suggested that I go to the Store and buy a license.
I must agree about support, she had absolutely no suggestions. And didn't know about Wait.

OK, the 2 days mitigates to some extent (but that delay is what the MS support person should have addressed - how stupid is it that they have an accepted key waiting to be activated then say it's fake? that's just mind-boggling - however, I stand by my suggestion of screen shots - it eliminates many perceptions.
Anyway, all's well that ends well.

macnab said:

Don't forget: I bought the software in South Africa. The box said for activation in Middle East and Africa. The product ID ended in MEA. I had to phone MS and get it activated manually because their computer said it is not usable in Africa. Something went wrong with the generation of that particular key.

Just as well for "stored" activations.

Are you sure? Please send me proof of the Middle East /Africa proviso - the activation mechanisms (which I'm well au fait with) has no regional specifications - product keys are broken down into decoded bits but none of those bits are regional.

In fact PM me the key - I would like to decode it.