So I've been having this problem for about 2 weeks.
I tried installing first Windows 7 64-bits, made the USB bootable and second Windows 10 Technical Preview and the following happens:
When I choose to go in Boot device selection menu, the USB does not appear.
When I choose to go into BIOS it is recognized, and I set it the primary boot device but after saving changes and rebooting, it is not recognized again.
Please help me.