Once it boots up in Win PE I'll fire up disk part and check, but I'm pretty sure it's possible. I've even emulated partitions in the past as external media to boot through them without requiring physical external media. I used to have a permanent WinPE partition in case things went wrong.
But if GPT doesn't allow active partitions, does that mean all partitions are automatically bootable by design?
MBR is not supposed to allow more than 1 active partition per physical disk. Now, I am not sure if some bit-level editing can be done to the partition table to make more than 1 appear, but that would have to be done with something like a hex editor manually writing values to specific sectors on the drive.
Not every partition on a GPT drive is bootable. Most (but not all) UEFI computers require the partition to be FAT32 formatted and won't boot from NTFS partitions. The partition then just has to have the proper UEFI boot files located in it. You can have more than 1 bootable partition on a UEFI system per physical drive - and that is true if the drive is MBR partitioned or GPT partitioned. Legacy BIOS (or CSM mode) only allows 1 bootable partition per physical drive, though.
But then how can you dual/multiboot off the same drive if only one partition can be bootable in MBR? I've always utilized partitions strictly for OSes.
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Ok so I'm now in WinPE and only C says it's active (disk part > partition details)
I cleaned the disk, but the MBR2GPT error continues. What gives? The entire capacity is now free according to disk part.
Dual/multiple boot is accomplished because there are multiple entries in the BCD file contained on the single active system partition. Each entry of the BCD file points to a different partition containing the OS to load.
You cleaned the disk. Therefore there is nothing for mbr2gpt to convert. According to the Microsoft document, mbr2gpt will not convert data drives. It will only convert system drives containing a partition marked as active that the computer is booting from. Since you did the "clean" on the drive, there is no active partition for the computer to boot from, therefore mbr2gpt is failing.
Since you "cleaned" the disk, the command you use to convert it to gpt is the "convert gpt" command in diskpart. The sequence will be:
diskpart
list disk
select disk # <- replace # with the actual disk you want to work on
clean <- this will erase the entire drive selected above
convert gpt
Then you can proceed to create or restore partitions on the gpt initialized drive.
That's what I ended up doing. I wasn't sure if it'd work without a system so I went ahead and installed Windows and checked and it is GPT now. All is good. Thank you for your help.
Can anyone point me in the right direction to create efi boot after cleaning drive and converting to gpt. I have gone through many sites with instructions but I have issue with some commands it doesn't recognise.
Brand new HP pavilion lap top and everything changed when I updated to win 10 pro. To cut the story short full disk is clean with no efi partition. I need to set up the HD from scratch
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