Thanks for all your efforts guys.
I can't answer half of the questions, because I don't know - but that video posted above, I followed it and wrote down the steps... went back several days, I can't remember how many, but enough and at least I have NXD back again (YES, NXD, on Windows 7!) I did have NX2, but as I have discovered how NXD works I am happy to leave it at that. If my new computer has got Windows 10 on it, then NXD will carry over, so I will have more continuity than trying to leant a whole new layout for just doing simple curve tweeks, essentially. The blemish removal tool is easy to use on the Nikon programs too.
Now at least I am back to where I was, now I need to work out how to use the RAW pictures off the drone. The Darkspace that Cyborg mentioned is weird but I it seems easier than Lightroom and I have been put right off Therapee, as you might imagine.
As I said on the drone thread, it isn't the physical flying aspect that I am going to have trouble with, it is the 'computer' aspects that I don't know enough about. Before I install anything else, I am going to find plenty of tutorials first, then decide which one. At least with NXD I have a book I can refer to for each step.