Aurora R7, won't boot a previously working Win10 system

An earlier occurrence of this fault was cured by unplugging peripheral items plugged into Mobo, then re-plugging one at a time until it rebooted. This time, repeating the procedure failed to work.

Now, on pressing and holding the BIST button illuminates the LED and sets all fans in motion. On releasing the button LED goes out and all fans stop. Any information would be gratefully received.