How can I use a local account in Windows 10?

Graeme was using a local account and needed Microsoft account to re-activate his copy of Windows 10. He would now like to go back to a local account

When I took the upgrade from Windows 7 to Windows 10, I continued to use my local account to log on. When I had to replace my motherboard recently, I needed a 30-minute chat (and remote access) with a very helpful Microsoft tech to re-activate Win10. Hmmm. To avoid that in future, I would like to use a Microsoft account, but only to get my system details on file in case I replace another critical component.

The problem is that I'm told I need to set-up a new local account after logging on with a Microsoft account. But I don't want to do that. I want to use my existing local account with the Microsoft one in reserve.