Ubuntu 9.04 Installation

[Rob]

Ok...here's a brain teaser.

I have tried twice now to install Ubuntu 9.04 to a Win XP box with the
following results.

Installation Attempt #1
The install appears to proceed normally to an external 500 Gig drive
(brand new) with Grub installed to HD0.  Previous installations like
this (to an older external drive) with Grub installed to HD0) worked
fine.  However, upon reboot after the Ubuntu installation, the system
halts on Grub error 15.  Fortunately, we had burned a Super Grub CD a
little over a year ago and that allowed me to boot to XP but not to
Ubuntu on the external drive.  Thinking it may be something unique to my
machine (an IBM/Lenovo), we called them since we have have on-site
coverage.  The technician came and installed a new motherboard (don't
know how he determined that was a problem but so be it.)  We rebuilt the
machine with the factory disks that came with it and I ran XP only for
about a week before attempting to install Ubuntu.

Installation Attempt # 1
Again, the installation appears to be proceeding normally to the
external 500 Gig drive with Grub installed to HD0.  Once again, after
installation completes and the machine is rebooted the following is
observed:

GRUB Loading Stage 1.5
GRUB Loading, please wait
Error 2

My only alternative is to was to reboot using the Super Grub CD to run
XP.  Would anyone have any ideas what may be going wrong here.  BTW the
Ubuntu CD I am using came from Linux Format magazine so it was not
downloaded or burned by me and I have no reason to suspect it is faulty.

Thanks in advance.
Rob