Can you boot into windows or stuck at repair?
If you can get to desktop, try this to fix errors:
right click start button
choose command prompt (admin)
type
SFC /scannow and press enter
this scans system files and may fix this behaviour
then once its finished, copy paste this into same window:
DISM /Online /Cleanup-Image /RestoreHealth
Once its finished, redo sfc /scannow again and restart PC
SFC fixes system files, DISM fixes SFC
If you stuck at boot, try this:
On another PC, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
change boot order so USB is first, hdd second
boot from installer
on screen after languages, choose repair this pc, not install.
choose troubleshoot
choose advanced
choose start up repair - this will scan PC and maybe fix this - will ask for logon info
if that doesn't help, you can try this to rescue data off PC: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/
Now if you can copy all your stuff off pc, the fastest way to fix this is a fresh install. Use the Win 10 installer and follow this:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html