"Bad shim signature" error when starting Windows

Windows 11 was no longer booting after I enabled Secure Boot. I was getting the following error message:

error: Bad shim signature

I was finally able to find a solution that worked for me:

1. Disable Secure Boot.
2. Boot into Windows.
3. Format a USB flash drive as FAT32.
4. Create the following directories on the USB drive: \EFI\BOOT.
5. Copy the file C:\Windows\Boot\EFI\SecureBootRecovery.efi to the \EFI\BOOT directory on the USB drive and rename it to bootx64.efi.
6. Boot the PC from the USB drive. Messages will be displayed on the screen indicating that Secure Boot has been restored. The PC will then reboot.
7. Allow Windows to boot normally. Log in and restart the computer.
8. Enter the PC's firmware setup (BIOS/UEFI) and enable Secure Boot, then reboot.
9. Windows should now boot normally with Secure Boot enabled.

Note: This solution worked for me. The exact steps may vary depending on the PC manufacturer and firmware configuration.