I think i read somwhere that USB 2 means it can access the external drive nearly as fast as an internal, and firewire a little faster than the usb2, its a vague memory though so don't quote me ;o).......I used poser on an external drive for a while, it was firewire and usb and it seemed to run fine, no noticable slow down and no real noticeable difference between the firewire and usb, but, noise was a real issue, the drive was an alloy one with a fan and it drove me mad, the plastic one was a little better but still to noisy so in the end i moved poser back to the internal and i do regular housekeeping using the external drives to store files as the internal drive is only 60gb....since then i've removed the fans from the drives and they seem to run fine so i may try it again.....another bonus is when you format the pc you can just drag your whole poser folder over to the external drive so its ready when format is done to drag back.....Steve