Q: Need help with external hard drive

Hi. I recently purchased an external hard (1 TB) drive from OWC that is compatible with my geriatric emac. I have followed their instructions on formatting and partitioning. I then used carbon copy cloner to clone my hard drive onto the external. I chose apple partition map, 1 partition. I selected the cloned external as the startup disk. It does not, however, show when I push the option key and restart. I am obviously not doing something right. I have next to no memory on the emac itself. I am not sure if I need to start all over or what?  Oh, almost forgot. I am connecting it via firewire. I tried to look and have seen posts similar, but not one that helped me. If one exists and you can steer me to it, I will be very grateful.