I bought the family upgrade pack for SL so we could upgrade my mother's, sister's, and my Macbooks but my sister lives about 9 hours away from us. So before I mail her our disc I wanted to make a copy of the disc to have here just in case. Also, to kill two birds with one stone I wanted a bootable image on my external hard drive for when I do my own clean install (happy, but not fully satisfied with the upgrade). What format do I need to have the partition of my external hard drive? Should I use the built-in disk utility to create my image? Which settings should I be using?