I just bought the 2012 model 13" MBP. Replaced optical drive with Samsung SSD. Installed El Cap. Everything works great. Now I wanted to have a bootable USB stick for recovery. Followed directions here to create Bootable El Capitan installer disk: http://osxdaily.com/2015/06/11/make-bootable-os-x-el-capitan-beta-install-usb-drive/ Except I used El Cap's version of Disk Utility. When I reboot with Option key down, I am presented with the selection of boot drives including the USB disk. If I select it, I can see the progress bar for a while, but before reaching the end of it, I get the ghostbusters sign. Any ideas?