Grub Error 17: Cannot Mount Selected Partition

i just tried to install ubuntu on a usb-hdd on my compaq 8510p. Everything seemed to work properly except i got the error:

Grub Error 17: Cannot Mount Selected Partition

the solution was pretty simple:
i switched to edit mode in the boot menue (select a boot-option from the list and press 'e')
then i tried to change the entry root (hd1,0)
changing to hd0,0 worked as expected

to make the whole step permanent i searched in /boot/grub/ for 'hd1,0' and found menu.lst

there i changed the entries for the main- and the compatibility- boot option to 'hd0,0' and restarted the computer

result: works as expected *hurray*