Boot with a Installation or Repair disc or USB drive – issue these from the Command
Prompt and hit ENTER after each.
C:
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd
After the above you may need to run Automatic Repair (even 2 or 3 times) – Option 5
here and run StartUp Repair to see if it helps.
bootrec /fixboot