Launch the BIOS setup utility by pressing the appropriate key or key combo during post.
Set your primary hard drive as the first boot option and disable the 2nd 3rd, 4th, etc.,
Don't disable or choose not installed for the devices, just disable them as a boot option so the Boot Device Priority screen only shows a single option, your drive containing your OS.
Secure the BIOS utility with a password that only you know (don't lose it or forget it) and you should be good to go.