I'm trying to make a USB partition work on MBR and UEFI. From what I've read on the forum, this will work If I use bootmgr and add a new entry for the grldr loader file.
I formated the disk as FAT32, modified the partition boot code to BOOTMGR, added the BCD files using windows bcdboot command: BCDBOOT c:\WINDOWS /s H: /f ALL . Copied over grldr and grldr.mbr. Added the grub4dos entry in the BCD store of BCD and EFI folders.
When I try to boot it it displays the error: Cannot load grldr because a file is missing.