Be careful! Select "I do Not Have A Licence Key" at the first time of being asked. Then when the upgrade has finished and you have run the Windows Update multiple times - even if it says "You re Up To Date"
Then go to automatically register in Windows 10 Update and security section. If that fails it will ask you for the Licence Key and at that point put in the key attached to the computer.
If you cannot read this because it has been obliterated IT IS VITAL you run Free version of Belarc Advisor before you start. Save the results or print out the result and the key will be there.
Post Back if you have any problems or PM me.