file not found grub rescue

I'm hoping you can help me with a problem that's worrying me sick, and which I caused myself. Here's two other facts I should mention: (1) I do not have a CD for my Dell Windows-XP desktop PC; it did not come with one. (2) I cannot access the internet through that desktop PC right now, but cable will be installed at my house next month. I'm entering this question from a laptop at the public library. (I do have dial-up service on my desktop PC, but I can only get to it through Windows, and I can't get to Windows right now, and only to rescue-mode in Ubuntu, so that's why I'm at the library.) I do have a Ubuntu 10.04 LiveCD.

Here's how I created my problem:

I wanted to be able to use Ubuntu on my desktop PC and also on my laptop. So I bought a portable external hard disk, and successfully installed Ubuntu 10.04 on it, while it was plugged into the desktop. Then, when I turned on the PC, I would first choose from a Ubuntu-supplied menu and then from a Windows-supplied menu. It worked fine.

But when I unplugged the portable from the desktop and then rebooted the desktop, I got:

error: no such device: 6afff52c-0175-4a2b-8e54-d87238027ada.
grub rescue>

So I plugged the portable in again, and tried to figure out how I could change things to be able to boot without the portable. At that time I mistakenly thought that I couldn't create a boot partition in Windows, though now I realize I could have. (I thought my PC already had four partitions occupied.) So instead, I simply used my 10.04 LiveCD to re-install GRUB2 on my C: partition. I now realize I shouldn't have done that, since my C-drive is filesystem ntfs and my portable-drive is filesystem ext4. Not only did I re-install GRUB2 to my C:\, but I removed the LiveCD as soon as grub-install told me "Installation finished. No error reported". Which I guess was too soon, because then I rebooted, and as it came down it displayed a page-full of errors, like:
.
.
[ 1288.401498 ] SQUASHFS error: Unable to read fragment cache entry [ 269.a66bd ]
[ 1288.403297 ] SQUASHFS error: Unable to read page, block 269a66bd, size abcc
/etc/rc6.d/s90reboot: 38: reboot: Input/output error

And then it hung there. I unfroze the keyboard by entering: alt + SYSRQ + R + E + I + S + U + B

Then a black screen appeared with the heading "GNU GRUB version 1.98-1ubuntu5" and some info about BASH, and then the grub prompt:

grub>

I was able to boot from there by using the "configfile" command. On Ubuntu (on the portable drive) I could see that there was still a /boot/grub directory, but now there was one on my C drive also! But doing "sudo update-grub" seemed to update the portable drive's grub.cfg file, instead of doing anything on C:\boot\grub. My C-drive's \boot\grub didn't contain a grub.cfg file (though it looked like it had all the .mod and .img files, and grubenv).

So, then I made my final bad decision: since doing a reinstall of GRUB2 (per the instructions in GrubHowto) on Windows had not removed the old /boot/grub directory from Ubuntu (the portable drive), I decided to delete the new /boot/grub directory from Windows (from my C: drive), and then do a "re-install GRUB2" on Ubuntu. I deleted C:\boot.

And then, when I rebooted, I came up at:

error: file not found.
grub rescue>

And nothing I do now seems to help. Can you suggest anything?

Humbly yours,

Susan Anderson

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Here's some additional information. I did these commands at grub rescue>:

set prefix=(hd1,1)/boot/grub
set root=(hd1,1)
insmod normal
      error: unknown filesystem
ls
     (hd0) (hd0,3) (hd0,2) (hd0,1) (hd1) (hd1,5) (hd1,1) (fd0)
ls (hd1,1)/
     error: unknown filesystem (and yet, that is my Linux partition)
ls (hd0,2)/
     dell/ $attrDef $BadClus $Bitmap $Boot $External .... (and all my C: files and directories)

In a terminal session from the LiveCD, I did "System > Administration > System Testing" and got a Checkbox Report.

Note that (hd1,1) equates to partition sdf1; they are my Ubuntu-aka-linux partition. The Checkbox Report says about sdf1:

E: ID_FS_TYPE=ext4
E: ID_FS_USAGE=filesystem

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A little more information: on Ubuntu, /boot/grub now contains only grubenv. Because I can't load the "normal" module, I can't try to reinstall GRUB2 again.

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Also: can you tell me if there is any document that completely explains the whole booting process? I feel like I'm working in the dark. I read the GrubHowto and KnowThyUbuntu, but they don't explain the whole thing, such as: this program calls this program, which calls this program...

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About the "unknown filesystem" message when I did "insmod normal": I also did "df -Th" and below are some of the columns it showed, for /dev/sdf1 (which is my linux):

Filesystem: /dev/sdf1
Type: ext4
Size: 685G
Mounted on: /mnt

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It's Tuesday March 13, 2012 now, and I'm back at the public library with my laptop. I've read another article that talks about the boot process; it's at http://askubuntu.com/questions/54981/... It's in answer to a question about uninstalling Wubi. I never installed Wubi, only the regular Ubuntu, and yet I have C:\wubildr.mbr, which is mentioned in my C:\boot.ini, and C:\wubildr. I think those files were added when I did "Install CD boot helper" when my PC wouldn't boot from the LiveCD, when I was trying to install Ubuntu in the first place. Since I never installed Wubi, but instead installed Ubuntu onto my portable external hard drive, is the boot process still going through boot.ini and then C:\wubildr.mbr? I wish I understood the whole boot sequence better. Maybe my C:\ubuntu\disks\root.disk is pointing to the wrong place?

I wondered if I could fix my problem by uninstalling Ubuntu--although I haven't yet found instructions on how to uninstall Ubuntu, only on how to uninstall Wubi. What I most wonder is: does the Ubuntu installation process first make a copy of the original Windows boot-process programs, so that it can rename them on an uninstall? Is an uninstall and then a reinstall possible?

If I can only get this fixed, I swear I will leave that portable hard drive plugged into my Desktop PC forever, and not try to make it optional. Thanks for listening.