Unable to boot GPT UEFI hdd on HP 800G1 tower

[handyguy88]

After creating a GPT formatted disk and copying/cloning my windows 10 system to  it, I am unable to boot from it,

I have enabled trusted platform, secure boot, fast boot, and disabled legacy boot. The drive does not show up in the list of UEFI devices, and therefore I am unable to boot from it.

I have two disks, so I can test coverting and booting from a GPT disk in preparation for Windows 11 install.

I created the GPT hdd using Windows DiskManagement followed by Macrium Reflect to clone the Windows 10 partitions.

I enter BIOS setup, change to Secure boot, and no disks are listed, so I cannot boot the GPT drive.

Did I miss something? Is the HP 800G1 not capable of booting UEFI HDD's ?

See the disk layout (disk 2 is the GPT disk) from Macrium.

Thanks for the help!

[Paul_Tikkanen]

The PC definitely supports booting from a GPT-formatted drive because I installed W11 in UEFI mode in my 8200 Elite CMT which does not even support secure boot but does have a UEFI BIOS.

I also have W11 installed in two Dell Optiplex business desktops with the Intel 4th gen core processors that are equivalent to the 800 G1.

I would just go straight to clean installing W11 on a drive rather than cloning it.

See this video for how to bypass the W11 hardware checks so you can install W11 on your 800 G1:

Set the partition scheme in the Rufus menu to GPT.

Windows 11 24H2 Install on Unsupported Hardware with Rufus

[handyguy88]

I plan to install win11 on top of win10, but first must convert disk to gpt/efi. I am unable to boot the disk as described above. Never shows up in UEFI list of bootable devices.

I have also done the following since first post:

• create partition efi size= 250
• format quick fs=fat32

Still does not show up in uefi boot list.

[Paul_Tikkanen]

When you cloned the original OS was that in GPT?

If not, then formatting the drive to GPT and then cloning the MBR partitioned W10 installation is just going to end up as an MBR partition.

I would start from scratch and convert the W10 OS from MBR to GPT then restart the PC go into the BIOS and disable legacy mode/enable secure boot.

Watch this video:

How To Convert MBR To GPT For Free In Windows 10

[handyguy88]

After cloning, it has an EFI partition and is labelled as GPT by diskpart.

There is no specific bios option to switch to uefi mode, so i presume it's just about setting secure boot, disabling legacy boot?

[Paul_Tikkanen]

That is correct.

If the drive is GPT, disabling legacy mode/enabling secure boot should get the drive to boot into Windows.

If you want to do an in-place upgrade to W11 24H2, the method in the video is by far the easiest way to do it.

How to Install Windows 11 on Unsupported PC in 2025 (New Easiest Method, No CMD)

[handyguy88]

Update March 13: I was able to convert one of my drives (alldata ssd) to GPT and successfully uefi boot. My primary drive (samsung evo) used the identical process to convert to gpt (executed ok), but does not show up as uefi drive, cannot boot. Process followed was:

1. Cloned samsung ssd to alldata ssd
2. Had 4 partitions, so delete unused recovery partition on (alldata ssd)
3. mbr2gpt /convert /allowfullos /disk:0 (alldata ssd)
4. diskpart shows disk to be gpt format (and an efi partition is now shown)
5. shutdown, bios set to uefi (no legacy) mode, alldata ssd is visible
6. booted alldata, everthing is fine.
7. Repeated the steps for Samsung ssd (all commands ran ok, diskpart shows as gpt, and extra efi partition is now shown)
8. Shutdown, bios set to uefi, samsung disk does not showup , and also cannot boot it as legacy disk either now.

So why did the alldata ssd convert and boot just fine, and the samsung does not?

[Paul_Tikkanen]

Unfortunately, I would have no idea.