Having just upgraded from Windows 10 from Windows 7, we wanted to share the experience to help others who have the same issues.
OK you will need time to upgrade its not in the background and you cant use your PC while its installing so start early and leave yourself few hours.
Start the upgrade from Windows 7. Follow on screen instruction.
We got to the stage where it had installed and was asking for a new Username for the PC. We entered the new username and pressed enter. On every attempt the screen froze, then turned blue then the PC restarted. We tried numerous options.
What worked for us was removing all attached USB devices. Especially the USB Wifi dongle/adapter.
After removing these we restarted and were able to enter a new username and continue installation/upgrade as normal.
This is a problem Windows 10 has with recognising USB devices that then hangs the installer.