Boot-Repair-Disk is a Linux-based bootable DVD designed to repair any Windows computer that won't boot. It is a tool for when all else fails. Available for 64-Bit here although they are rarely updated at the same time.
Boot-Repair-Disk primarily aims to fix boot issues, including screwed-up partitions, damaged MBR (Master Boot Record), and more. It can be handy to make these repairs if you don't have a bootable copy of Windows.
To use Boot-Repair-Disk, burn it to a DVD or use a program like Rufus.
Now boot and select your language and internet, if available. Then choose "Recommended repair" and reboot. You can find some advanced options on the left before you run it. If your computer won't boot, and you've exhausted all possibilities, this might be what saves you.