Install Windows 10 in UEFI mode and in MBR mode

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BuonaForchetta
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Joined: 18. Feb 2021, 16:44

Install Windows 10 in UEFI mode and in MBR mode

Post by BuonaForchetta »

I have installed Windows 10 on VirtualBox and the disk is partitioned as MBR so I believe in Legacy mode, correct me if I'm wrong.
Now I would like to install the same system (Windows 10 Pro 64 bit) in UEFI mode with a GPT type partition card.
Can you explain to me how to proceed?
I can partition the disk in GPT (there are many software on live cd that do their job egreggiamente) but I can not set the UEFI mode.
If I set GPT and then I try to install Windows 10 I get MBR.
thanks
scottgus1
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Re: Install Windows 10 in UEFI mode and in MBR mode

Post by scottgus1 »

MBR can be used with BIOS or UEFI. GPT can only boot from UEFI, but can be accessed after an MBR disk is booted on a BIOS PC.

To use EFI instead of BIOS, got to the VM's System settings, Motherboard tab, Enable EFI checkbox.

The OS you install also has to be compatible with EFI. The OS needs to handle setting up the virtual disk for MBR or GPT.
BuonaForchetta
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Joined: 18. Feb 2021, 16:44

Re: Install Windows 10 in UEFI mode and in MBR mode

Post by BuonaForchetta »

scottgus1 wrote:MBR can be used with BIOS or UEFI. GPT can only boot from UEFI, but can be accessed after an MBR disk is booted on a BIOS PC.

To use EFI instead of BIOS, got to the VM's System settings, Motherboard tab, Enable EFI checkbox.

The OS you install also has to be compatible with EFI. The OS needs to handle setting up the virtual disk for MBR or GPT.
I don't understand the use of the word BIOS in your answer.
I only know of two installation modes (Legacy and UEFI). The BIOS, on the other hand, is the software within which you can choose the two options (Legacy or UEFI).
EFI, on the other hand, I don't know what it is, it's a new term for me.
In any case, in your answer you do not explain to me how to access the VirtualBox virtual BIOS within which to set Legacy or UEFI before installing Windows.
scottgus1
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Re: Install Windows 10 in UEFI mode and in MBR mode

Post by scottgus1 »

BuonaForchetta wrote:The BIOS, on the other hand, is the software within which you can choose the two options (Legacy or UEFI).
Personally I am unfamiliar with using the term 'BIOS' and 'Legacy' that way.

As I have heard the word 'legacy' used, it means 'the old way, not the new way'. For computer booting, the old way is BIOS, the new way is UEFI.

None of the motherboards I have used had a choice to use BIOS or EFI. But there might be some out there that do.

Virtualbox has that choice, in the 'Enable EFI' checkbox. Checked, the VM will boot in EFI mode, enabling GPT or MBR boot disk usage. Unchecked, the VM will boot in BIOS mode, and only MBR boot disks can be used.
BuonaForchetta
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Joined: 18. Feb 2021, 16:44

Re: Install Windows 10 in UEFI mode and in MBR mode

Post by BuonaForchetta »

I did not know that on VirtualBox you could not install Windows 10 on GPT, what a pity.
Thank you so much for the information.
mpack
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Re: Install Windows 10 in UEFI mode and in MBR mode

Post by mpack »

BuonaForchetta wrote:I did not know that on VirtualBox you could not install Windows 10 on GPT, what a pity.
Where did you get that from? Of course you can install Windows 10 on GPT, in VirtualBox.

And just on a pedantic note: a BIOS is a BIOS. That BIOS may be modern UEFI compatible or it may be a legacy BIOS supporting MBR booting and partitions only (no GPT). VirtualBox did not invent this limitation, it is the defining characteristic that separates the two.

In VirtualBox you enable the EFI VM setting if you want the BIOS to emulate the former. You would use the latter when dealing with a guest OS that doesn't know GPT from Adam. I.e. DOS, Win98, XP etc - all the way up to Win7. I believe that Win7 doesn't support booting from GPT, but it can read from GPT.
scottgus1
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Re: Install Windows 10 in UEFI mode and in MBR mode

Post by scottgus1 »

mpack wrote:a BIOS is a BIOS. That BIOS may be modern UEFI compatible or it may be a legacy BIOS
Ah, nice nuance, thanks for clarifying this, Mpack!
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