How to Disable Windows Boot Manager
Windows Boot Manager appears each time you start your computer when you have two or more operating systems installed. The boot manager gives you the opportunity to choose the operating system to boot into. When you remove an operating system and return to only one, Windows Boot Manager may still appear each time you boot your computer. To disable this feature, you need to go into your system's settings.
Click the Windows "Start" button in the lower-left corner of your desktop.
Type "msconfig" (without the quotes) in the search field above the button. Hit the "Enter" button on your keyboard.
Click the "Continue" button on the window that appears. Select the "Boot" tab.
Highlight the operating system that you want to boot. Click the "Set as default" button. Click the "Apply" button and then press the "OK" button.
Click the "Restart' button.