Have you tried booting into Safe Mode with Command Prompt Mike?
If so and you can get in, try running CMD as Admin and using the DISM commands, namely the DISM Restore and Cleanup commands (not much point using the file checking one) when you know there's an issue. The DISM commands should replace Windows Key Files with perfect versions from the Web or a Backup file. If that fails, you could try Windows Restore as I think Windows Updates create a restore point but whether that works from Safe Mode, I'm not sure. I don't know if there's any way of creating a bootable restore file to allow you to access restore points from outside windows.
I think there's also a way of accessing rollback to last known gogd config on bootup, but you'll need the web on that one. Even then, when I used it in the past, it was very hit and miss. I'd regard this one as a last resort as it could stop you booting entirely.
Personally I use Shadow Protect SPX these days but it's a bit late once you already have an issue.