I trying to change the default loading os to windows Xp . So read article on "How to set windows as default when dual booting Ubuntu and start a KDE/Kubuntu GUI application as root user" ;but in vain. when I try to edit grub.cfg it gives following error "The document could not be saved, as it was not possible to write to /boot/grub/grub.cfg. Check that you have write access to this file or that enough disk space is available". Is there any trick to do it by terminal.