[lug] How to recover after installing Broken Grub?

[siegfried]

Since we have a shortened install fest this time, I thought I would do a
little experimentation in advance.

I just bought a 250GB USB drive from CompUSA for $60 and tried to install
Debian Etch on it.

This is a desktop windows machine I borrowed from my client. The
installation asked me if I wanted to install GRUB and I said sure -- why
not?

Well, now I cannot boot windows. With the default BIOS settings, it tries to
boot from the USB drive first and that fails. So I go to the BIOS and tell
it not to boot from removable devices and try again. GRUB comes up but does
not list the windows partition -- only the debian partition on the USB
drive.

So I try to boot from the debian partition and it says 

ALERT! /dev/mapper/sheintze-vpn-hp-root does not exist. Dropping into shell.
BusyBox v1.1.13 (debian 1:1.1.3-4) Built in shell (ash)
Enter 'Help' for a list of built-in commands.

How do I fix the problem? vi works so I guess I can edit.

Should I be able to edit the GRUB settings so it can boot windows without
the USB drive attached? I hope so. Otherwise, I will want to remove GRUB and
I don't know how to do that. How do I do that?

ls tells me there is a /dev directory but no /dev/mapper directory.

Any suggestions?

Thanks,
Siegfried