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

ABuBr71N84Uu · Post by **ABuBr71N84Uu** » Sat Jan 10, 2026 8:46 pm

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 · Post by **jWFynlKj** » Sun Jan 11, 2026 1:22 am

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 · Post by **p4A4P** » Sun Jan 11, 2026 2:38 am

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

ffRUO3Ws · Post by **ffRUO3Ws** » Sun Jan 11, 2026 2:58 am

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 · Post by **N0y4N6** » Sun Jan 11, 2026 7:05 pm

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