I can't BELIEVE how much difficulty I'm having with this. On a 2nd gen. Air, with Mountain Lion, I need to boot via USB and run a program FROM that same USB, i.e. NOT from the system drive, which I want to partition-shrink and create. I resorted to a Linux thumbdrive with GpartEd, which almost worked, but failed upon disk checking. In any case, there are a couple of native Mac apps that I wish to run, but they can't be booted from--or even run from--the system drive. How, then, to prepare a bootable USB source that can run its own app (other than those included in recovery)?