Installin XP and Vista images on same PC

Hello,
I have an XP ghost image of a PC that had only XP installed.
Also, I have a Vista ghost image of another PC that only had Vista
installed.
Now I need to install both images on two partitions of a new PC.
So, I put Vista image on partition 1 and XP on partition 2.
Vista loads ok but I can't get XP to load. I followed the instructions given
at http://support.microsoft.com/kb/919529
But when I select XP from the boot up menu I get an error message:

Invalid Boot.ini file
Booting from C:\Windows

then I got black screen and nothing else.
I can't edit boot.ini because the only partition that loads is vista and
from there it does not allow me to modify boot.ini.

Any idea how to solve this? or maybe use a different approach...

I use this for testing purposes, I have to install/unistall vista and XP
everyday for testings and I want to make the install a little faster by
using images.

note: both XP and Vista images have been fully tested working alone and they
work perfect.

Thanks
e.