Peter, yes you are a chap after my own heart! The archaeological process of recovering and re-installing all my files and programs, not to mention 'where did I put that serial number?', has been great fun. And this time I've documented everything. I'm quite touched to find how many vendors enabled me to re-download software I bought years ago - A2A, Aerosoft, REX, ASN, Flight 1 to name few, and even provided updates.
Sorry to hear about your Flight1 issues. Maybe I had the advantage of having a completely clean Win 10 Pro and FSXSE instal. Once I'd installed Flight1's 'agent' it found UTxUSA and Gex, which I bought in 2015, and re-downloaded them for me. I think their installer has been re-worked since I first installed them, as it was exceptionally straightforward this time. If you could get every vestige cleaned out, inc. in the Registry, and start from scratch like I did, maybe you'd have success? You could always ask for help on SimForums.com - I built my previous Haswell rig following the advice of NickN whose "Bible" was exactly that when it came to optimising FSX, and I think he's still around. The Man.
Brian, you should put your stuff together and get it made into a 'sticky', it would such a help to folks like me.
Anyway, I've just made a first flight in my A2A Cub from a (UK2000) hand-modelled Nottingham airport (a mile from where I live) over VFR GenX photoscenery using REX4 + soft clouds and AS Next weather engine. As I stepped round to the garage to fire up the PC it was starting to snow. In FSX as I advanced the throttle under an overcast grey sky - it started to snow! Scary white-out cloudbase at 1000 ft. Awesome!
Alan