If you are new in Linux, especially for you who still use dual-boot with Microsoft Windows or other operating systems, I will share my knowledge on how to change default boot for GRUB. There are a lot of GUI applications to do such thing but knowing the basic concept is important if you want to know more about Linux. Before we get started, please take a closer look at the picture below:

OK! Let's make an assumption, we have five entries in GRUB numbered with 0 until 4 which number "0" (Ubuntu) is default boot for GRUB. It means that if you don't do anything when this screen appears, the "0" entry will be selected to boot. Now, we want to make the "4" (Windows XP) entry to be a default boot for GRUB. To do such thing, we have to edit "/boot/grub/grub.cfg" file, simply type the following command:
  • sudo gedit /boot/grub/grub.cfg
New Gedit window will be opened and shows the content of "/boot/grub/grub.cfg". Search for statement set default="0"!

Do you find it? All you need to do is changing the "0" number to "4". It makes the "4" entry (Windows XP) set to default boot for GRUB. Don't forget to save your work and reboot to see the changes.

Regards :)