Problem switching to GPT

Here's the rundown on creating a system partition to boot from. You can use whatever partitioning program you desire to meet the following requirements:

1. You need at least 100mb unallocated on the drive to create the system partition in. If you are going to boot in legacy bios/CSM mode, the drive must be MBR partitioned. If you are going to boot in UEFI mode, the drive can be either MBR or GPT partitioned.

2. You need to create a primary partition in the unallocated space.
If your drive is MBR partitioned, the diskpart command is:
create part pri size=100.
If your drive is GPT partitioned, the command is:
create part EFI size=100. Size=100 sets the size of the partition at 100mb. Set it lower than 100mb and you risk an upgrade of one version of Windows to the next version of Windows failing (IE: 1803 to 1809). Rarely is more than 100mb needed. You can change the size if you want, or leave the size off the command to use all the remaining contiguous free space on the drive. An EFI partition cannot be created on an MBR drive, it has to be a PRImary partition. UEFI booting does not required an EFI system partition type to boot from, it only requires a FAT32 partition to boot from, and it cannot be a logical partition.

3. If you are going to boot in legacy BIOS/CSM mode, the partition must be active. The diskpart command is simply:
active. The partition can only be marked as active on an MBR partitioned drive. If you are going to boot in UEFI mode and the drive is MBR partitioned, I suggest you set it as active anyway, but not required.

4. Format the partition as FAT32. Diskpart command is:
format fs=fat32 quick.

5. Assign the partition a temporary drive letter. Diskpart comand is:
assign letter=W. You can use any unused drive letter.

6. Exit diskpart with the command:
exit

7. Back at the command prompt, the command to make the partition bootable is:
bcdboot C:\Windows /s W: /f ALL. In the command prompt environment, your Windows may not be C: drive. Change C:\ to whatever driver your Windows actually is. Change W: to whatever drive letter you assigned to your new system partition. /f ALL means the partition is bootable in all modes: legacy BIOS, CSM, UEFI, assuming all other requirements are met.

So...that proves my point that GPT is not required to boot in UEFI mode. If it was, the /f ALL switch could not work, because the drive must be MBR partitioned to boot in legacy BIOS/CSM mode. The /f ALL switch can only work if the drive is MBR partitioned AND the system partition is formatted as FAT32,

Exactly what one would expect from Dartmouth. A clear concise answer that worked first time. Splendid. The 'ALL' option is not included in the list of bcdboot examples that appear but it worked.
Many thanks,

meditek said:

Exactly what one would expect from Dartmouth. A clear concise answer that worked first time. Splendid. The 'ALL' option is not included in the list of bcdboot examples that appear but it worked.
Many thanks,

Agree, great post by NavyCMDR...

The "bcdboot" documentation does explain the "/f" switch and its options, also provides examples at:

BCDBoot Command-Line Options | Microsoft Docs

Cr00zng said:

Agree, great post by NavyCMDR...

The "bcdboot" documentation does explain the "/f" switch and its options, also provides examples at:

BCDBoot Command-Line Options | Microsoft Docs

I was referring to the examples that popped up when I was doing the job- I missed a space. There were 5 or 6 but none included the ALL with the /f. All goes to show one should RTM first!

Anyway having got what I wanted I made the mistake of setting Fast Boot which prevented bios access requiring a bios reset to get back in. What are the 'other ways' of accessing the bios in these circumstances? Main reason I wanted UEFI was the faster boot!

Caledon Ken said:

You can access on some machines through Advance Startup Options, which can be accessed by holding shift key down and clicking restart.

Boot to Advanced Startup Options in Windows 10

Notice the box for UEFI Firmware Settings option under the heading Advance Options

Also check your BIOS options, some force a time delay, at least that is what I have on my Asus.

No force time delay on my Bios but your other option works fine. Having said that the fast boot didn't seem much faster but now I have every thing running as planned thanks to everyone's kind advice here. My I5 8400 cpu is running happily at 3800MHz; memory at 2666 (1333x2) at 38C with standard fan. Not sure about all these leds winking at me in various colours but it amuses my grandkids.

NavyLCDR said:

Here's the rundown on creating a system partition to boot from. You can use whatever partitioning program you desire to meet the following requirements:

1. You need at least 100mb unallocated on the drive to create the system partition in. If you are going to boot in legacy bios/CSM mode, the drive must be MBR partitioned. If you are going to boot in UEFI mode, the drive can be either MBR or GPT partitioned.

2. You need to create a primary partition in the unallocated space.
If your drive is MBR partitioned, the diskpart command is:
create part pri size=100.
If your drive is GPT partitioned, the command is:
create part EFI size=100. Size=100 sets the size of the partition at 100mb. Set it lower than 100mb and you risk an upgrade of one version of Windows to the next version of Windows failing (IE: 1803 to 1809). Rarely is more than 100mb needed. You can change the size if you want, or leave the size off the command to use all the remaining contiguous free space on the drive. An EFI partition cannot be created on an MBR drive, it has to be a PRImary partition. UEFI booting does not required an EFI system partition type to boot from, it only requires a FAT32 partition to boot from, and it cannot be a logical partition.

3. If you are going to boot in legacy BIOS/CSM mode, the partition must be active. The diskpart command is simply:
active. The partition can only be marked as active on an MBR partitioned drive. If you are going to boot in UEFI mode and the drive is MBR partitioned, I suggest you set it as active anyway, but not required.

4. Format the partition as FAT32. Diskpart command is:
format fs=fat32 quick.

5. Assign the partition a temporary drive letter. Diskpart comand is:
assign letter=W. You can use any unused drive letter.

6. Exit diskpart with the command:
exit

7. Back at the command prompt, the command to make the partition bootable is:
bcdboot C:\Windows /s W: /f ALL. In the command prompt environment, your Windows may not be C: drive. Change C:\ to whatever driver your Windows actually is. Change W: to whatever drive letter you assigned to your new system partition. /f ALL means the partition is bootable in all modes: legacy BIOS, CSM, UEFI, assuming all other requirements are met.

So...that proves my point that GPT is not required to boot in UEFI mode. If it was, the /f ALL switch could not work, because the drive must be MBR partitioned to boot in legacy BIOS/CSM mode. The /f ALL switch can only work if the drive is MBR partitioned AND the system partition is formatted as FAT32,

hi sir it didnt work for me i was able to boot from my ssd because i have created boot partition using your method
but EFI boot didnt work this massege still appearing "default boot device missing or boot failed insert recovery media and hit any key"
Thank you.

A screenshot of disk management would help:
Disk Management - How to Post a Screenshot of

NavyLCDR said:

A screenshot of disk management would help:
Disk Management - How to Post a Screenshot of