When you configure Windows in a dual-boot set-up, the operating system displays the Windows Boot Manager screen when you turn on the computer, allowing you to select which version of Windows to load. This screen persists even if you stop dual-booting and eliminate the second Windows installation from your computer, adding up to 30 seconds to the amount of time needed for your computer to start up. By editing your system configuration to remove the 30-second wait, you can remove the Windows Boot Manager screen and load your preferred version of Windows automatically when the computer starts up.
Click the Start icon in the bottom corner of the screen. Right-click the "Computer" or "My Computer" menu item, and then click "Properties."
Click the "Advanced System Settings" link on the left side of the window in Windows 7 and Windows Vista. If you are running Windows XP, skip this step.
Click the "Advanced" tab, and then click the "Settings" button under "Startup and Recovery."
Click the drop-down menu under "Default Operating System," and select the version of Windows that you want to load when the computer starts up.
Remove the check from the box next to "Time to display list of operating systems." Alternatively, change the number of seconds to "0."
Click "OK" twice and restart the computer. When the computer reboots, the selected version of Windows loads automatically without displaying the Windows Boot Manager screen.