How to boot to non-EFI Windows installation (sometimes called Legacy boot)

[Pete333]

Hi Guys,

colleagues, thanks for all the good in your work, pls I need your guidance:

The concerned rig is a Schenker Work 15 E21 I use now (BIOS ver. 1.07.16RTR4, EC EC_1.07.07A) - I would like to boot from an external HDD with a non-EFI Windows 22H2 installed. Can you help pls?


some details + what I've already tried to do:
I have Windows 10 Pro 22H2 fresh testing installation on an external HDD (MBR, NTFS, non-EFI installation) connected using simple USB3-to-SATA interface (I've also tried one of RAIDSONIC ICY BOXes, by the way it uses UASP if it is important, and is connected to the comp through USB3 cable). This Windows10 installation was originally done on other computer. Now I would like to boot this Work15 using the mentioned Win10 (as it is not Windows-To-Go type of installation, let's ignore the fact that its HAL is set to work with other HW, and so that when this Win10 would start to boot it would probably "shout" that this is not the original HW it was installed on - never mind for now, I need to get it to at least start to boot, and if that starts, I can correct eventual HAL issues). But I can't see this external HDD non-EFI Windows installation in BIOS's Boot Manager, nor I can boot it using BIOS's Boot From File functionality. In this Work15 there is an NVMe SSD in it, and I have set the BIOS to ignore its Windows loader.

The question is: how can I switch the Work15's BIOS from UEFI to Legacy mode? And, generally, can I boot a non-EFI Win10 from an external HDD this way, on such Work15 (with the BIOS mentioned)?

feel free to use tech language where necessary, I am in IT for 25+ yrs

Thanks a lot for your guidance, best, Pete

[XMG Community]

Hi there,

non-EFI boot is not supported anymore on current laptop platforms, including your 2021 system with Intel's Tiger Lake platform.

Windows 10 Pro 22H2 fresh testing installation on an external HDD (MBR, NTFS, non-EFI installation) [...] This Windows10 installation was originally done on other computer.

Would it not be simpler to convert your disk to GPT first?

[1] How to Convert MBR to GPT or GPT to MBR Without Losing Data in Windows 11/10/8/7
https://www.easeus.com/partition-manager-software/convert-mbr-to-gpt-gpt-to-mbr-using-cmd-without-losing-data.html

And then employ one of the various current methods of booting Windows from USB?

Methods may include:

[2] https://www.easeus.com/backup-utility/create-portable-windows-usb-drive.html

[3] https://www.pcmag.com/how-to/how-to-run-windows-10-from-a-usb-drive

[4] https://www.geckoandfly.com/32030/bootable-windows-pe-recovery-repair/

Best Regards,
Tom