I had to do a clean install of Windows 10 Fall Creators Update, as the upgrade install messed up everything in Steam.
Nothing other than Steam worked. My Steam games, 3DMark, PCMark 8 and PCMark 10 didn't work at all. Steams fixes didn't solve it, so hopefully it will all work with this install.
I'm still on my GOG games now.
Then Origin, Ubisoft, GameSessions and then Steam.
I'll probably do my 2 Forza games before Steam, too.
Software will be sometime late Wednesday or Thursday.