By the installation of Linux on a Windows installed machine the default loading OS becomes the Linux. If the user want to change the default one we have to edit the boot loader file of linux OS.
The name and disk location of the GRUB configuration file varies from system to system; for example, in Ubuntu, Debian GNU/Linux and openSUSE the file is stored in /boot/grub/menu.lst while Fedora and Gentoo Linux uses /boot/grub/grub.conf. Fedora also provides a symbolic link from /etc/grub.conf to /boot/grub/grub.conf for FHS compatibility reasons and other distros can establish symbolic links to the three locations.