Am failing at the first hurdle as I can’t get any of those diagnostic tools to run - end of a long day so quite possibly an attack of the blondes… when I try to run from command prompt I get the message “The subsystem needed to support the image type is not present”?

No new software installed but I think I had a Windows update, an Avast update and possibly a Firefox update not long before I started having issues booting. Originally it would boot Windows but then hang trying to open any program. Now it won’t even boot Windows.