So I was trying to fix my non-booting Windows by installing GRUB. I marked the Windows data partition (/dev/sda4) as BIOS_GRUB in GParted and did and update-grub /dev/sda, with the idea that grub MBR code will execute Windows bootloader.
However grub took the /dev/sda4 partition and used it for it's core.img
And now by Windows NTFS partition is gone. Or is it? I read that the core.img file only has like 32KB which totally overwrote the NTFS partition header. But the data must still be there. I tried to use ntfsfix -n /dev/sda4 but unsuccessfully:
Mounting volume... NTFS signature is missing.
Attempting to correct errors... NTFS signature is missing.
Failed to startup volume: Invalid argument
NTFS signature is missing.
Trying the alternate boot sector
The alternate bootsector is usable
The startup data can be fixed, but no change was requested
Volume is corrupt. You should run chkdsk.
No change made
Without touching the computer I would like to get other peoples opinions on how to fix this. So is there a way to fix the NTFS header that was corrupted by core.img?
Here is my boot info https://pastebin.com/aRKMuFTY
note that only /dev/sda is relevant, am currently on /dev/sdc Manjaro I moved the BIOS_GRUB flag away from /dev/sda4