Is it possible to install Windows 10 on MBR using UEFI?

Question

I need to move Windows 10 from my HDD to my SSD but apparently I have to use a GPT instead of MBR. The real problem is: in this SSD I already have installed Linux in a second partition, so if I change partition table I'll have to backup all my data and reinstall Linux with all the things. Is there a way to install Windows 10 on MBR without switching from UEFI to Legacy?

Solution 1

The real problem is: in this SSD I already have installed Linux in a second partition, so if I change partition table I'll have to backup all my data and reinstall Linux with all the things.

No you don't; converting between MBR and GPT does not require touching actual partitions at all – the only thing you rewrite is the table itself. Both formats work at the same level (fundamentally they just list sector start–length pairs), and the conversion procedure mostly looks like this:

1. Run gdisk /dev/sda which will convert in memory, then use w to write out the GPT table to disk. (This will also replace the original MBR table with a protective MBR.)
2. Reinstall your Linux bootloader, so that the EFI NVRAM boot entry will have the new UUID of the 'EFI system partition' (which I assume you already have).
3. Proceed with Windows installation in UEFI mode.

Solution 2

Install Windows first and don't worry about it being MBR, then open Cmd as Admin after installing:

1. DiskPart → List Disk → Exit
   

2. # Where 1 is the Windows 10 disk number reported by DiskPart:
     Mbr2Gpt /Validate /Disk:1 /AllowFullOS
   
   # If successful:
     Mbr2Gpt /Convert /Disk:1 /AllowFullOS
   

3. Reboot and open UEFI firmware settings → Disable CSM [Legacy boot]

Mbr2Gpt only works on system disks and supports a maximum of three partitions (I think due to Windows creating an EFI partition), but you can create as many partitions as you like after converting.

Comments

[Ramhound]

This is a very good answer. It actually answers the author's question.

[bg117]

Thanks @JW0914!