Hold on to your Windows 7, 8 and 8.1 collections
As late as the early 2000's, HP Very High Frequency equipment from the 1960's was selling for almost five times its original cost. Why? Because that great old stuff was part of many assembly lines, laboratory and industrial processes/proceedures and it would have cost a fortune to rewrite the specs as to make it all work with newer stuff, which wasn't any better, at least for the purposes at hand.
So, I'm going to make sure that even when I'm forced to adapt to Windows 10, I'm going to make sure to save all the Windows 7 stuff I'm using now. Maybe someday it, too, will be worth five times what I paid for it.