From:

From: http://windowsreport.com/windows-10-automatic-repair-couldnt-repair-pc/

Choose Troubleshoot > Advanced Options.
Select Command Prompt from list of options.
When Command Prompt appears, enter the following lines and press Enter after each line in order to run it:
bootrec.exe /rebuildbcd
bootrec.exe /fixmbr
bootrec.exe /fixboot
Some users are also suggesting that you need to run additional chkdsk commands as well. To perform these 
commands, you need to know drive letters for all your hard drive partitions. In Command Prompt you should 
enter the following (but remember to use the letters that match your hard drive partitions on your PC):
chkdsk /r c:
chkdsk /r d:
This is just our example, so keep in mind that you have to perform chkdsk command for every hard drive 
partition that you have.

Restart your computer and check if the issue is resolved.

Also: http://marcushall.net/dokuwiki/doku.php?id=software:microsoft:windows:boot#mbr_fix

From: http://www.windows10forums.com/articles/reset-windows-10-when-windows-wont-boot.14/

Please be warned that by resetting your system all 3rd party apps will be removed, however you can 
choose to keep personal data (i.e. Documents) during one of the steps. This is effectively a clean 
install which will resolve severe problems with Windows.