You are saying that dual boot Windows / Linux is sometimes possible with Secure Boot enabled, sometimes not possible, and that depends on which PCI cards are plugged in the motherboard, correct? Does that imply that disabling Secure boot is impossible with the current bios of Asus Z97? Just trying to understand. Are there any guides on how to dual boot with asus motherboards? I have successfully installed ubuntu and am using it now, but only way to boot to it is to insert the Ubuntu bootable USB and select it as boot device in the Bios.