help after automatic update restart now BSOD error BSOD error message 0xc000021a Windows 10 stuck in loop

[stephbruce]

My Laptop installed automatic updates for Windows 10 and then I clicked to restart it. I am now getting a blue screen error
Your PC ran into a problem and needs to restart error code: 0xc000021a
It then tries to carry out an Automatic Repair by restarting but then it just goes back to the original blue screen.
Microsoft advise after automatic repair to select Troubleshoot > Advanced options > System Restore but I received an error message saying it had failed.
Tried auto repair and a reset and system restore but they have all failed. Now stuck in a crashing loop. Also tried to boot in safe mode and this has failed.
Tried all the suggestions on microsofts help page and now wish I never allowed it to restart.

Laptop is a Toshiba Satellite C50 running Windows 10.

Thank you.

 

[Colif]

Cause

This error occurs when a user-mode subsystem, such as WinLogon or the Client Server Run-Time Subsystem (CSRSS), has been fatally compromised and security can no longer be guaranteed. In response, the operating system switches to kernel mode. Microsoft Windows cannot run without WinLogon or CSRSS. Therefore, this is one of the few cases where the failure of a user-mode service can shut down the system.
Mismatched system files can also cause this error. This can occur if you have restored your hard disk from a backup. Some backup programs might skip restoring system files that they determine are in use.

I think only option is a fresh install. It sounds like the users are corrupted and almost all options outside a clean install would fail as they all use your settings

Now I assume that laptop didn't come with win 10 so your only choice is download this on another computer and create a windows 10 install USB or DVD: Windows 10 Media creation tool

NOTE: if you have anything you want to copy off laptop, you can use this method to get them: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/

Once installer is made, change boot order to match whatever you made
Boot installer and do this: http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html