start up loop

My computer using windows 7 64 (professional i think) recently auto shutdown to apply an update. While this was happening the computer accidentally was switched off. When i restarted everything seemed fine until i got past the 'starting windows' screen with the flag (straight after the bios...

I had numerous problems with win10 so I tried to uninstall to an earlier version(win 8). I am caught in the start up loop. No system disk to boot from. No valid system restore point. Start up repair is ot working. HDD diag is ok. Toshiba satellite laptop.