BIOS/UEFI and Windows 8/10
Installation in BIOS mode:
If you want to setup a multi boot system with Windows 8/10 and Boot-US then you need to install Windows 8/10 in the BIOS mode.
In this case the boot process of Windows 8/10 is similar to that of Windows 7. On an UEFI motherboard the BIOS mode is often called
CSM (Compatibility Support Module) mode.
Installation in UEFI mode:
Boot-US does not support the UEFI mode. If you install Windows 8/10 in the UEFI mode then you cannot use Boot-US.