Thanks to all of you for your observations.
Underclocked suggests an ingenious approach which I'll probably use if and when I decide to try out Windows 10 (which I don't need. It's only for educational reasons that it interested me).
I'm all for Windows 7 all the way till 2020 ... or later if people stick with it as they do today with XP.

There are still about 180 million XP users (12% of pc users) out there as at Sept. 1st!!!
Watch out for the "stab in the back" approach Microsoft has by automatically upgrading Windows 7 users to Windows 10 without warning them.