My Windows 10 upgrade from 7 has taken 4 days and is now looping

[WPCentral Question]

Toshiba Salellite L750D, 100M broadband connection whioch was running at about 54M.
It is now at a point where I can login to 10 but now appears to be in a loop. It displays a Stonehenge wallpaper but the screens keeps going blank and refreshing and occasional shows the desktop for a few seconds before looping. Why did I bother