If you no longer require the other operating system, you can remove it via Disk Management. Press "Windows-Q," or point to the top right side of the screen and select "Search" from the Charms bar.

Select the operating system you wish to boot on startup, such as "Windows 8 Home." Uncheck the box labeled "Time to display list of operating systems." Click the OK button and reboot to ensure ...

Then uncheck Time to display list of operating system. Reboot, and you’ll find that the menu is gone. You may want to remove the Windows 7 partition as well, but that could be dangerous.