If you installed the second Windows OS computer, then when you start the system you need to choose the right and wait for 30 seconds before it starts or press Enter. It is quite inconvenient, so the choice of operating system and the parameters of its start it is necessary to correctly configure.
Open control Panel: "start" - "control Panel". Locate and open the line, "System", select the "Advanced" tab. On it find the section "startup and recovery" and click Settings.
You will see the settings window of the operating system boot. You may want to remove the selection window of the operating system at the start, removing the tick from "Display list of operating systems". In this case, it will boot that system that is loaded by default. In the line "Operating system that is loaded by default", you can choose any of your desired OS.
Although the above-described variants, a selection menu is better not to disable, even if you use only one operating system. In case of problems with the main OS you can always boot from the second, to keep important files or to restore the primary OS. When disabled, the menu selection that you will not.
To download wait 30 seconds, change the line "Display list of operating systems" time from 30 seconds to 3. Three seconds is enough, if necessary, to choose another OS. In the line "to Display recovery options when needed" leave of 30 seconds. You can call the menu with the recovery options by pressing during system startup F8. If the operating system in some whena rank fails to boot, select recovery options "last known good configuration". Very often this is enough for a successful upload.
In that case, if you have installed with Windows and Linux, the functions of the loader itself usually takes Grub the most common bootloader on Linux. To configure the load – onwithmeasures to select which OS will boot by default, you can go two ways. The first is to edit the grub configuration file.cfg. The concrete configuration options depend on the version of Linux, look for them online. And second, more simple way – install startupmanager. It will help you in graphical mode to configure the dual boot.