Yes you're right - This isnt exactly related to my original thread but I forget when I owned 2 machines I once needed to do a reinstall on the older one (MB) but didn't have the install disks so tried using the DVD restore tool (from a newer MBP DVD) to access my backup on an ext drive to no avail !
However I did use the install disk from another 3rd machine (older MBP to access restore tool & restore from backup!
So now basically have same disk image on current MB unibody as on the MBP (santa rosa) i used to use.. (i bought MB 2nd hand and needed to reinstall it with my stuff on)