The problem I discovered with a recent MacBook Pro is that the machine will not boot with an "older" OS than the one it comes with (10.6 in this case), so having 10.5 available still won't work. NikonScan still runs fine on 10.6.7, but opens with a warning that there is a minor error of some kind. I put the original 10.6 that came with the machine on an external HD, and booting from that, it runs without any kind of warning, so I am ok for the moment with this machine, but I see the day coming... (I'm assuming that even if I were to go to 10.7, I could still boot in 10.6, but will have to see how that goes. If only Parallels or VM Fusion could use firewire, I could still run it on XP....