I took 2 storage HDs out of my Mac Pro and stuck them in this external HD which I just bought. When I plug it in to my Macbook Pro and turn it on, nothing happens. It all lights up and the harddrives churn for a little bit, but nothing shows up on the desktop or in Disk Utility. What am I doing wrong? I have tried FW400, FW800, and USB2.0. I'm new to external enclosures, so tell me if there is some song and dance routine I need to perform to get it to show up.