Windows Partition Not Bootable

Solution 1:

Is there a way to fix it without formatting the windows partition and reinstalling windows?

Yes. You don't want to format the windows partition. You will need to boot from a Windows install disk, but rather than a clean install, you'll want one of the following two options:

1. Boot repair with bootrec /fixboot and/or bcdboot
2. A repair install (like an upgrade) that preserves your existing files and registry entries, rewriting the OS files, OS registry entries, and bootloader

Note that the original Windows install disk may not be suitable for performing a repair -- if you've installed any Feature Updates (prior to Windows 10 these were known as Service Packs), then you want to create install media matching your current version.

And an OEM Recovery Disk is definitely not what you want, these may be pre-programmed to wipe the entire disk (not just the Windows partition) and replace the contents with a factory image.