"my concern is more with the physical space limitations on a hard drive." I maxxed out a 60 gig hard drive with only 3 extra runtimes-- I grant you Downloads was huge! And the PP one even huger. Fire wire is a good alternative option-- I would not trust USB 2--never seen it live up to it's speed claims. There is a tiny hesitation with my Maxtor Firewire but I run all my important runtimes off of it. And plenty of room for scratch and backup. EM