sudo cp /boot/grub/menu.lst /boot/grub/menu.lst_bak
[sudo] password for USERNAME:
sudo gedit /boot/grub/menu.lst



explanation:
sudo cp /boot/grub/menu.lst /boot/grub/menu.lst_bak
>>copy original file to backup

[sudo] password for USERNAME:
>>confirm superuser (type your password here---you won't see any asterisks, but it's working)

sudo gedit /boot/grub/menu.lst
>>open the file for editing ("sudo" may be optional)