My apologies. I assumed you had more experience with GNU/Linux. I also apologize for misreading your post. So, I need to modify my suggestions, as well as be more detailed in the instructions so that you will understand what to do.
In re my first (erroneous) reading of your post, I make this revision to my response:
You probably installed grub to the MBR of the internal drive, which points to the rest of grub on the external drive. With the external drive unplugged, grub can't proceed because it can't find the rest of it's files on the external drive.
You should have installed grub to the MBR of the external drive.
For example:
Let's say the internal drive was shown as /dev/sda and the external drive was shown as /dev/sdb (it may have been shown as /dev/hd0 and /dev/hd1).
You should have chosen to have grub installed to the MBR of /dev/sdb so that when the external drive was re-installed in the older box, grub would then be in the proper location, with pointers to the rest of grub on that drive.
Quote:
You want me to boot my windows xp, unplug the external(I'm guessing as windows is loading
|
No. I want you to boot with the external drive plugged in, and boot into Ubuntu on the external drive.
Quote:
and then.... you lost me. Could you explain how to open a terminal and su to root, update grub and re write MBR.
|
In your gnome menu, look in the Utilities menu for terminal or console. Or, in your system tray, look for an icon that looks like a computer monitor (terminal). Click on the menu entry/icon to open a terminal. You will see the famous (infamous?) command line (with prompt). Su is the command to switch user (when the user name is given as a parameter to the command) and to switch to super user (root or sys admin) if no user name is given. You will then be prompted for the root password. Enter the password.
Once you are root, type the command grub-install /dev/sdb and press enter. That will install grub on the MBR of the external disk to point to the rest of grub on the external disk, then shut down.
Re-install the external disk in the old box and boot up. You should see a grub menu with both Ubuntu and Windows.