Thanks to all who replied. You helped me understand a little better why .NET Framework lives in my laptop, and even a little understanding is contentment in old age.
I'm particularly grateful to Phone Man and NoN for the guidance that earlier versions have been hiding there all along, albeit well camouflaged for a non-expert. Version 3.5.1 is where Phone Man said; it is checked, though the tick is grey. Version 2 can likewise be reached as NoN said; both entries had been disabled and I reset them to manual. So I guess I'm now properly set up unless anyone tells me otherwise.
I'm pleased that Cinderelli found the link useful but you may need to reset Version 2 as advised by NoN.
Thanks again guys.