If you're not using grub idk but here would be some potential troubleshooting steps for Arch or any distro that doesn't change grub (pretty sure Debian has its own specific set of tools for grub)

Mount your Windows partition, install os-prober, enable OS probing in /etc/default/grub, and run grub-mkconfig -o /boot/grub/grub.cfg

You might wanna mount the ESP partition too if it isn't already

[–] PM_ME_VINTAGE_30S@lemmy.sdf.org 4 points 8 months ago (1 children)

My understanding is that GRUB (using the chainloader command) successfully calls the Windows bootloader when I ask it to run Windows, but I think the Windows bootloader is corrupted. It is corrupted to the point that I cannot even use the recovery disk or install disk to fix the system.

I think a Windows update broke it. I have OS probing enabled, and it successfully detected (and booted into) the Windows partition back when I first installed Debian. It still detects the Windows partition, but Windows bluescreens with an error message that I can't remember off the top of my head, but both Microsoft's support forum and other resources basically indicated could only be fixed with a reinstall. Debian, of course, boots just fine.

I ran chkdsk on the Windows partition with the Windows Recovery Disk and I also checked the partition in Gparted, and both processes found no errors. The Windows partition is perfectly readable from Debian.

So I'm inclined to believe that Windows broke itself.

[–] ProgrammingSocks@pawb.social 1 points 8 months ago

If that's the case, then yeah. Rescatux might have a tool that can fix it but I don't really bother fixing Windows installs usually. I would still try regenerating /etc/boot/grub.cfg but if you've done that already it is probably Windows' fault