I'm trying to upgrade my Windows 10 PC to Windows 11, but I have a dual-boot set?

[ABuBr71N84Uu]

Agreed. This happened to me. I fixed the 0xc000000f by booting from the Windows install USB and using the command prompt to rebuild the BCD. Let me know if that works.

[jWFynlKj]

Yeah, the "bootrec /rebuildbcd" command from the USB is the way to go, but you'll probably need to reinstall GRUB from a Linux live USB afterwards to get your dual-boot back.

[p4A4P]

Same here. Agreed. Also, before you reinstall GRUB, make sure Windows is fully booted and fast startup is disabled in the power settings.

[ffRUO3Ws]

Can confirm. I had the same problem. I fixed the 0xc000000f error by booting from a Windows installer USB and using the startup repair option first.

[N0y4N6]

You could also try recreating the GRUB bootloader from your Linux live USB, which often fixes the Windows bootloader overwriting it.

[1e8MgG7Oha]

+1 Yeah, that's a solid fix. Just make sure you boot the live USB in the same mode your Linux install uses, like UEFI or Legacy, to avoid any mismatch.

[vBnilXuaAX]

Can confirm. You could also try using a tool like EasyUEFI from within Windows to manually add the Linux boot entry back. Another option is to just reinstall GRUB from your Linux live USB, which often sorts it out cleanly. Hope that helps.

[8599Yf383]

You could also check your BIOS boot order to make sure Windows Boot Manager isn't overriding everything. Another option is using the `bootrec` command from Windows recovery to rebuild the BCD.

[7gJOAy5DMMu]

You could also try booting from a Linux live USB and reinstalling GRUB from there. Another option is to use a tool like EasyBCD in Windows to add a Linux entry back to the boot menu.