I have installed Ubuntu on a partition of my external usb drive. Since I had problems with grub2, I have uninstalled it and installed grub1. But then the usb drive didn't boot anymore, and I am forced to the limited shell of grub1. If I write manually
kernel (hd0,4)/vmlinuz-2.6.31-15-generic root=/dev/sdb4 ro quiet splash initrd (hd0,4)/boot/initrd.img-2.6.31-15-generic boot
then Ubuntu is loaded, but if I execute the commands
root (hd0,4) setup (hd0)
as explained at http://www.gnu.org/software/grub/manual/html_node/Installing-GRUB-natively.html#Installing-GRUB-natively, next time I boot from usb I am forced again to the grub limited shell. How can I restore a working grub?