I hate the commandline, even though I got my start there. As I age, my fingers
do not fly across the keys as fast and I am ham-handed as it is. Add to that my
memory is not as good as it used to be and you can see why I prefer the GUI.
Fortunately, I seldom need the commandline and when I do I am usually content to
copy and paste someone else's work.

Grub can't find the drive it is looking for because the BIOS and grub are
approaching things from different sides. Grub uses ordinal numbers (starting at
zero) and counts up. The BIOS goes by settings so that the first boot device is
fixed. If things are changed in BIOS or in the jumpers then grub can become
messed up or if a device is taken out of the sequence then the same thing can
happen.

The solution is to not mess with your system once it is set up or to use a
chainloader. In order to fix things you will have to experiment a bit and then
edit grub menu.lst to make the results permanent.

You can temporarily change grub by pressing e on any line. Then you can change
the numbers. Keep track of what changes you make and only change one at a time.
When you have changed one thing press b to boot and see if the change gets grub
to load the kernel.

I would press e while on the OS that I am trying to load unsuccessfully. Let's
say it is Ubuntu.

You might see something like this:

title Ubuntu hardy, kernel 2.6.24-16-generic
root (hd0,1)
kernel /boot/vmlinuz-2.6.24-16-generic
root=UUID=80bee887-3479-4ce6-8209-a87267b8a3c5 ro quiet splash
initrd /boot/initrd.img-2.6.24-16-generic
quiet

Go to the line root (hd0,1) and press e. Then change the second one to a zero
so that it reads: root (hd0,0) then press b. If it boots then you will have to
edit menu.lst to change that line permanently. To do this type: sudo gedit
/boot/grub/menu.lst and edit the line. Then save it. (If you are using Kubuntu,
substitute kate for gedit.)


You may find that the line already reads root (hd0,0), so in this case try root
(hd0,1). If this does not work then try changing the first number which is for
the drive. The second number is for the partition. If you have two drives with
one partion on each change the first number. If you have more than one partition
on one drive then change the second one. This is not rocket science but trial
and error.

I'd go with what Linux Canuck says, except that in my case, GRUB saw
the external drive as:

root (hd1,0)

I had installed it on the first partition of the external drive.

When booting, then the boot drive is drive zero, so I had to edit the entry to:

root (hd0,0)

Once you are up and running, take note of what you edited.

Then from a terminal enter:

sudo gedit /boot/grub/menu.lst

Then make the same edit that you did in Grub, whichever it turns out
you needed. Save and it makes the change permanent. Hey presto, no
more booting problem.

From then on, you will boot just fine. You will probably find all the
other entries in menu.lst skewed as to drive number also. Edit them
all, if you want all the choices to work.

I posted, I shut
down the computer(not a restart), and brought it back
up and grub took off like it is suppose to. I did do
it several times during the time I was on as I had to
switch back and forth between Ubuntu and Win, and
worked fine. I am keeping these messages just encase
it happens again.