Windows 10 install reverts a GPT disk back to MBR

Having been frightened into ditching Windows 7 for Windows 10, I decided to buy a Western Digital 1TB SSD and perform a clean install of Windows 10 Pro using the MS Media Creation Tool onto a USB drive. I assumed that, as I was using a virgin SSD, Windows would default to creating a GPT disk. I ended up with a MBR disk. After some research I was convinced that GPT, being more modern, was a better bet. I therefore used Diskpart to clean the disk and convert to GPT. Using the List function I confirmed that the SSD was now a GPT disk. Having reinstalled W10 I find that Windows has converted my drive back to MBR before installing. My motherboard is about 6 years old but working fine. Using F2 on startup I get to the UEFI setup utility so it is a UEFI board. There is no option of choosing legacy or UEFI booting but a slightly confusing set of options including UEFI: TSSTcorp CDDVDW or AHCI P1: TSSTcorp CDDVDW (though I only have 1 DVD drive). The SSD is marked as AHCI P4: WDC etc.
I read somewhere else on this forum that Windows will create a MBR or GPT drive depending on what type of drive the installation software is booted from. I also read that you cannot make a USB pen drive GPT which seems to imply that it is impossible to use GPT if you insall from a USB drive. So, I have two questions: How can I get Windows to install onto a GPT drive and, secondly, is it really worth all the bother?
Any advice would be much appreciated.
Thanks, Phil

Thanks for taking the time to respond Dalchina. 12 tells me to go to 14. 14 tells me to 'Delete all partitions/volumes on the Drive'. I did that with Diskpart clean. However, Windows still converted the drive back to MBR before installing.

Did you note that in step 14 it states "Your motherboard must support UEFI 2.0 or later to be able to install 32-bit and 64-bit Windows 10 with UEFI" ?

It's possible that your MB does not support this.

In all honesty, I would trust the selection that Windows makes here.

However, that said, I'd like to look into this a further. I see that your system configuration lists an Asrock motherboard. By any chance could you post the exact model number here?

To do a Clean Install of Windows (7, 8.x or 10) as UEFI-GPT you must:
- Have a UEFI BIOS set properly.
- You must install 64 bits OS.
- You must boot the installation disk as UEFI, not Legacy.

Important: Detach ALL other disks (SATA or power cable), leaving on only the target disk.

Insert the Win 10 installation disk (USB or DVD) and start the computer. During POST, hit (pulse many times) F8 to launch the boot options menu.
Select the Win 10 installation disk that has UEFI on the option

Please update the specs in the "My Computer" section:

System Specs - Fill in at Ten Forums
In the left corner below in your post you find 'My System Specs'.
After clicking it you can find a link a little below that says 'Update your System Spec', click on this link to get to the page where you can fill in your system specs.
System Info - See Your System Specs - Windows 7 Help Forums

Include PSU. cooler, case, peripherals and anything attached to the computer by wired or wireless (mouse, keyboard, headset, printer, xbox, USB wireless network card, etc.)


Check if Windows 10 is using UEFI or Legacy BIOS

hsehestedt,
I am installing a 64bit version of Windows 10 Pro. The motherboard is ASRock H61M-DG3/USB3. I have checked through the manual and this only states 32Mb AMI UEFI Legal BIOS with GUI support. It does not mention UEFI 2 so maybe that is the problem? The installation is Windows 10 Build 18363 it also shows as 1909. Windows System Information reports "Legacy mode". I cannot see any way to force booting in UEFI from the Bios settings. However, I can see that Legacy USB and Legacy USB 3.0 support are enabled. In ACPI Configuration CSM is enabled. The Windows Media Creation tool downloaded Windows setup onto a Toshiba 8Gb UB 3 pen drive. Is there anything else that would help?
Cheers, Phil

- - - Updated - - -

Zbook, apologies - system specs updated

CiderPhil said:

hsehestedt,
I am installing a 64bit version of Windows 10 Pro. The motherboard is ASRock H61M-DG3/USB3. I have checked through the manual and this only states 32Mb AMI UEFI Legal BIOS with GUI support. It does not mention UEFI 2 so maybe that is the problem? The installation is Windows 10 Build 18363 it also shows as 1909. Windows System Information reports "Legacy mode". I cannot see any way to force booting in UEFI from the Bios settings. However, I can see that Legacy USB and Legacy USB 3.0 support are enabled. In ACPI Configuration CSM is enabled. The Windows Media Creation tool downloaded Windows setup onto a Toshiba 8Gb UB 3 pen drive. Is there anything else that would help?
Cheers, Phil

- - - Updated - - -

Zbook, apologies - system specs updated

It's not from BIOS settings. You must launch the boot menu options as soon as the computer starts. To do so press F8 repeatedly.

CSM is Compatible System Mode. That is for Windows 7. Turn it off.

Megahertz, thank you. I thought I was looking in the BIOS settings. If I plug the USB pen drive with Windows setup on it into the USB port and then reboot via the boot options (F11 on my machine), I have USB: Toshiba Transmemory and UEFI: Toshiba Transmemory listed. So I could use the latter entry. The USB drive is an MBR device. Does that matter?
Thanks, Phil