I have a older white 24" imac. The question I have is will it make a diff if I run the whole thing on the external drive. I have heard of some good things about it. I was thinking of some sort of firewire 800 drive. I only have a 250 gig in it now. Would it be in my best interest to have the internal drive replaced with a speedier one or a fast external. Or is it even possible to run all on the external drive. Thanks MC