I had the same problem last year with a friends board that kept trying to bios boot a non-existent install of Ubuntu , i used the above guide with a USB Live-disk that worked perfectly to remove it.
So I bought this motherboard which came as standard boot via uefi from a system that is no longer on the PC!
The HD that had Fedora was formatted and installed on another machine.
But the boot persists with Fedora.
When I press F10 to select the startup shows in the list as Fedora priority and then my HD!
When I do not press the F10 I leave the boot executed by order that is in the BIOS that is prioritizing the HD it says that there is no boot partition
Whenever I connect the PC, I have to press F10 and choose hd to start win10.
Here's something to try: Go into BIOS Setup and disable UEFI. Save the configuration as you exit from BIOS Setup. When it completes POST and presents BIOS splash screen, hit F2 to go back into BIOS Setup again. Re-enable UEFI. Save the configuration as you exit from BIOS Setup. When it again completes POST and presents BIOS splash screen, hit F10 and check whether the entry has remained in the list (it should have been cleared out).
Hope this helps,