XP Pro, Vista Ulti, Vistaboot ver 3.3 and Acronis true image ver.11

I installed Vista first and got XP installed and both are running (not
at the same time) with the help of Vistaboot. I've been using Acronis TI
for a long time and like it. I need to know if I make an image of either
Vista or XP will I be able to install just that OS and all associated
with it. OR should I do an image of both OS drives. Both OSs are on the
same physical hard disk. I 'd like to be able to image XP and if I have
to recover, then Vista and XP will still boot. Guess it has to do with
the MBR and I'm not really up on that. If any more info is needed let me
know and I'll try and supply it.

Thanx for any help,
Bob