Win10 installation broken presumably after Windows Update

I've installed Parallels Desktop 12.1.2 as a trial on my existing boot camp partition running Win10.
Things seemed to be working ok until Windows suggested that I update using Windows Update.
I had an error message saying something like "prevent changes to master boot record" or some such. I'm now stuck in a reboot loop, where
the error message is "CRITICAL_PROCESS_DIED", and all attempts to repair Windows fails.

I've sent the error report using the "Send technical data" in the app, but no answer.

 

Are you able to start native Bootcamp Windows partition without an issue?

 

No, native boot camp doesn't work either. It fails as described in the first post. In order to get back to OSX I have to press and hold the Option key during startup.
Now this was a trial that has since expired. Will removing Parallels fix the problem ?

 

Looks like the Windows operating system is corrupted because of the Windows update. Please repair Windows 10 natively on Boot camp and check how it goes!