Re: Problem / Solution
"The key on the bottom was accepted as Gospel, and activation was without hitches or drama."
Make sure you have a system image for next time. I put mine on DVDs - two copies. An activated fresh install normally only needs 3 or 4.
The original Windows on a PC usually contains a generic key for the OEM - not the one on the PC's label. The latter is an OEM one-off and any attempt to do a second install with it later will be rejected.
Even a "retail" licence seems to have re-install restrictions. I was recovering a PC that had had a motherboard failure - using a copy of the hard disk for safety. It needed a re-authentication - so far so good. Then I swapped to a bigger disk - and it refused to let me re-authenticate. Three months later I tried the same disk again - and this time it worked. It looked like there was a limit on how many times you can re-authenticate inside three months.