UPDATE - 15.12.14: My celebrations were premature. The pop-up returned. I am working on it and will post a further update when I have a solution.
UPDATE 2 - 17.12:14 If all else fails try the simple approach. This is the solution posted on the Microsoft website... and it worked, I think...
To activate by using a direct connection
Open Windows Activation by clicking the Start button , right-clicking Computer, clicking Properties, and then clicking Activate Windows now.
If Windows detects an Internet connection, click Activate Windows online now. Administrator permission required If you're prompted for an administrator password or confirmation, type the password or provide confirmation.NB if Windows detects that your copy of Windows is valid this may be as far as you need to go. If your activation time has expired it may be necessary to enter the product key as below.
Type your Windows 7 product key when prompted, click Next, and then follow the instructions.
First message screen...
2nd screen, seen if you click the Resolve option...
3rd screen shows "Buy Genuine Windows" tab when it opens, this is the "Troubleshoot" option...
If your Windows activation period has expired your computer functionality will be reduced and the desk top will become black with a permanent message shown in the bottom right-hand corner.
To make a system repair disc, click the "Start Button" and type System Repair in the search box, click "Create a System Repair Disc" option and follow the instructions. You will need a blank CD to hand.