OEM boards sometimes have strict Secure Boot settings. Enter the BIOS (usually by pressing or Delete repeatedly upon startup). Look for "Secure Boot" settings and try disabling them or switching to "Legacy" mode if you are installing an older GPU.

Manual Updated — Acer H67h2 Ad Motherboard

OEM boards sometimes have strict Secure Boot settings. Enter the BIOS (usually by pressing or Delete repeatedly upon startup). Look for "Secure Boot" settings and try disabling them or switching to "Legacy" mode if you are installing an older GPU.