Install Windows 10 in Legacy Boot mode

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I am trying to install Windows 10 in legacy mode on a drive that uses MBR. I have a Windows 10 installation ISO file from which I created a bootable USB drive. However, USB drive only boots in UEFI mode, and not in legacy mode (I alternated between the two options in the BIOS menu). When the Windows installation process is started in UEFI mode, it cannot install Windows to a MBR drive. Hence I need to create a bootable USB drive that can start in legacy mode. Is this a limitation of the ISO file that I am using? I have tried many different utilities (Rufus, UNetbootin, etc..) to create the bootable USB.

If this is the case, where can I obtain a Windows 10 installation ISO (I have a license key) that can be used to create a legacy bootable USB drive?

Gleb Billig

Posted 2017-08-31T19:01:32.450

Reputation: 21

"Hence I need to create a bootable USB drive that can start in legacy mode." - You already have done that. If you want to install on a MBR partition enable Legacy Mode and then boot to the installation media you have created. If you want to install on a GPT partition then disable Legacy Mode. The best way to install on either GPT or MBR is not to have any partitions on the drive. "here can I obtain a Windows 10 installation ISO" - Use the Media Creation Tool offered by Microsoft. – Ramhound – 2017-08-31T19:20:19.923

https://superuser.com/questions/1108085/where-can-i-get-a-clean-iso-of-the-windows-10-anniversary-update-build-14393-o – Ramhound – 2017-08-31T19:23:12.623

When I enable Legacy Mode and boot to that installation media, my computer shows a black screen and then return to the "selection boot media" menu. However if I switch to UEFI mode, I am able to boot from the USB drive. – Gleb Billig – 2017-08-31T20:56:21.000

Don't know what to tell you. I am able to boot to the same installation disk created with that tool in either Legacy Mode or UEFI Mode. – Ramhound – 2017-08-31T21:16:24.980

What tool are you using to create the bootable media? – Gleb Billig – 2017-08-31T21:46:42.087

I already told you, the Media Creation Tool, see my prior comments – Ramhound – 2017-08-31T21:48:08.120

Answers

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After digging deeper into my BIOS settings menu, I found there is an option to enable support for booting from USB in UEFI mode. For some reason, enabling this option suddenly made it possible to boot from USB in Legacy mode as well.

Hence the issue was not with the .iso file nor with the USB booting utilities.

Gleb Billig

Posted 2017-08-31T19:01:32.450

Reputation: 21

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I have tried many different utilities (Rufus, UNetbootin, etc..) to create the bootable USB.

Rufus does not create dual BIOS+UEFI USB disks by default – it has an explicit selection for that. Therefore if the USB stick successfully boots in UEFI mode, it is UEFI-only and you need to select "BIOS (CSM) mode" in Rufus.

user1686

Posted 2017-08-31T19:01:32.450

Reputation: 283 655

Asked: 2017-08-31T19:01:32.450

Viewed: 41 935 times

Active: 2019-08-26T15:19:32.530