I downloaded Windows 10 from the net on 30 March. All went fine until I tried to start it from sleep mode. All I got was a repeating succession of solid screen colours (the Microsoft ones, actually) one after the other. The only way I knew how to stop this was to hold the power button for 5 seconds - less than ideal ! - and then do a full shut-down and re-start. How do I stop this happening please ?