The multiboot setup I wanted is now working perfectly, it almost went too easy once I understood what was going on with the EFI NTSF driver, the \EFI files on the Windows OS partitions, the boot menu, etc. Thanks again to everybody.
I'm now working on automating the drive letter rearrangement etc. in PE (like I do now in BIOS/MBR systems and disks).
I know this is going a bit off-topic, but as there haven't been other "beginner" questions in this thread over the last few days, and some might still remember my scenario of using Grub4UEFI to boot from different OS setups on different partitions (without using MS BCD menus etc), I wonder if somebody can shed a bit of light on this:
- I have a test setup now of (1) EFI system part 100mb, (2) 4x 50gb Windows OS, (3) Data partition (I want the D: letter for this one), (4) One more partition (Also for data, specifics not important, drive letter E:).
When I'm using one of the Windows setups, I simply remove the drive letter to the other OS partitions, this seems to work just fine.
When I boot with PE, I would expect the EFI part to NOT have a drive letter, and this is indeed the case.
But the 4 OS partitions also don't get a drive letter, I don't mind that at all (saves me a lot of trouble removing the letters anyway), but I don't understand WHY this is?
The next partition (which I ultimately want to be D:) is automatically assigned C: (the first letter) in PE. This is expected, but only because the 4x OS partitions are skipped.
The next partition (becomes "E:") is assigned "D:" (which is expected at this point).
The only thing that's different on the OS partitions is that they now all have an "EFI" folder (needed for booting with Grub4UEFI, see earlier posts by Alacran in this thread). This doesn't seem likely to be the cause of skipping them for a letter assingment, because I can remember cases where one of the OS partitions DID get a C: letter in PE, but I can't remember the specifics of that case.
So, it boils down to this: Why are these partitions skipped when assigning drive letters in PE? PE is supposed to be "clean" on every boot, so no entries about registry settings or OS specifics should be taken account on a new boot?