It won't work. I'm using an external drive, bootcamp says it's successful. Upon rebooting however, I'm greeted with 'no boot device found'. I've used multiple drives, different USB ports, different ISO, different bloody everything. I've got as far as option + reboot. It sees my drive as 'wininstall' but will not boot from it. I read somewhere I NEED an external optical reader but I can't see that being true. I'm not buying one just to install windows anyway.