I'm a new mac convert, and I'm pretty sure I know the answer to this, but I have an external HD that I used with my old PC. When I connect the drive to my mac, I can read/copy files to my mac, but not write. Is this because the external HD is in a Windows format and Macs cannot write to this, thus I'll have to reformat the external HD? Or, is there something that I don't know about yet that I can do to allow me to write. Thanks for your help.