Today I installed the latest upgrade to windows 10 on my desktop machine and after completion of the installation the system booted up, apparently normally, until the scene from the cave looking out to a sandy beach appeared at which point to went into a hang mode. The normal user name and login slot did not appear and it did not respond to the alt-ctrl-del command so I can't get to Task Manager etc. to try to recover the system.
I have tried to do a cold start several times but to no avail.
I would very much appreciate your expert advice on how I should proceed to recover the system.