Windows

Reinstall Boot Manager

These instructions also work if: - Bitlocker is activated - the EFI partition is not displayed as a volume.

1. Delete EFI partition using diskpart:

   REM select correct disk (replace x with the id of the disk)
   list disk
   sel disk X
   REM select efi partition (replace n with the id of the efi partition)
   list part
   sel part N
   REM delete efi partition
   del part override
   

2. Create new EFI partition using diskpart:

   REM create efi system partition
   create partition EFI size=200
   REM format partition as fat32
   format quick fs=fat32 label="System"
   

   If more disk space is required to create the fat32 system (16 MB is not enough!), the C: partition can be reduced in size:

   REM select C:\ (replace n with the id of the root partition (probally the largest one))
   list part
   sel part N
   REM create more free space (200mb)
   shrink desired=200
   

3. Assign letter for EFI partition using diskpart:

   REM select efi partition (replace n with the id of the efi partition)
   list vol
   sel vol N
   assign letter Y:
   

4. Reinstall Bootloader

   bootrec /rebuildbcd
   bootrec /fixmbr
   bootrec /fixboot  # works even if you get access denied...
   bcdboot c:\Windows /s Y: /f ALL
   

5. Reboot