UEFI install? The quirks seem to say yes...

For the third time: Storage Boot Option Control may need to be Enabled to boot a flash stick. It may even pertain to disk. I would have it enabled for Legacy or both.

Read the manual for your BIOS on the mobo's Support Downloads webpage to see what those Secure boot states are needed for and if they apply for you. Study fully the other settings to familiarize yourself with them.

Boot override choices are most often if you want to temporarily boot from media or another choice than the Boot Priority order, and should be the same as the BIOS Boot menu key choices which every mobo has, but isn't accessible in Windows 8 except via the Advanced Boot options.

gregrocker said:

For the third time: Storage Boot Option Control may need to be Enabled to boot a flash stick. It may even pertain to disk. I would have it enabled for Legacy or both.

Sorry, should have caught that and reiterated. But I did mention it here. It was disabled when I captured the screenshot, but I've tried it on Legacy, Legacy first and UEFI first with the same results. I've let it stay at Legacy Only.

Read the manual for your BIOS on the mobo's Support Downloads webpage to see what those Secure boot states are needed for and if they apply for you. Study fully the other settings to familiarize yourself with them.

Yes, I have been keeping the pdf manual up on another screen for reference. These manuals aren't always clear though. However, I've just finished posting a thread in the Gigabyte UK forum (no U.S. forums available...). So hopefully, there will be some insight from that end.

I'll post back when I find out something conclusive.

Thanks!