Can't boot Windows from secondary mass storage bootable devices on UEFI-based computers

This article describes an issue in which a Unified Extensible Firmware Interface (UEFI) based computer can't boot Windows from the second bootable media.

Assume that two Windows bootable media devices such as a CD-ROM or other USB Mass Storage Device (Device Logical Unit) are attached to a UEFI-based computer. The computer boots from the first media even if you set the second media as the first bootable media or choose to boot from the second media.

For example, suppose the first bootable media is Windows Server 2016 and the second one is Windows Server 2019. When you try to boot the computer from Windows Server 2019, the computer boots from Windows Server 2016 instead.

This is by design. The current Windows OS versions do not support Device Logical Unit–Vendor-Defined Messaging Device Path. A Windows ISO image will boot only when it is mounted from the primary bootable Device Logical Unit mass storage device.

Third-party information disclaimer

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.