How to remove the flash blip of the dual boot screen at startup

Hi All,
I recently acquired a used Lenovo Y580 laptop. The previous owner had a dual boot system in place (now removed and only running win7 ultimate.)

The issue I have is when the system is turned on, a less than 1/2 second blip of the dual boot screen flashes on the laptop display, disappears and then win7 boots up. This "dual boot flash of the screen" is really annoying.
A search on how to resolve this stated to go into the Control Panel/System/Advanced system settings and then into the settings of startup and recovery to uncheck the "time to display list of operating systems".
I found it was unchecked already.

There is no other OS to boot on.
So why does it flash a quick glimpse of the dual boot dispay?
I'd like to remove this.

Thank you.