Thank you for joining the Intel communities.
It took me some time to come around to this post and to be able to help you; I really apologize for the delay.
In this case, I recommend accessing the BIOS and press F9 on your keyboard to set the BIOS to defaults, then make sure the UEFI is checked and also the legacy boot, after that is done, press F10 on your keyboard to save the changes and exit.
Your system will restart, when you get the prompts press F10 on your keyboard and that will take you to the F10 BIOS, once your there select the bootable USB and follow the steps to install Windows 8.1.
That’s it; like that you will be able to install Windows.
Again I really apologize for the delay on this post and I hope your issue can be resolved with the information provided.
Thanks and regards!