Change GRUB's default boot setting to windows

• watch windows menuentry name

$ cat /boot/grub/grub.cfg

   ...
   menuentry "Microsoft Windows XP Professional (on /dev/sda1)" {
   ...

• change GRUB_DEFAULT

$ sudo vi /etc/default/grub

   GRUB_DEFAULT="Microsoft Windows XP Professional (on /dev/sda1)"

• update grub.cfg

$ sudo update-grub