I am trying to get this straight in my head in case I want to reinstall Lion for testing and other purposes without having to keep a Lion partition around at all times. This is specifically for computers that came with Lion since one cannot create a bootable USB Lion install these by re-downloading Lion from the app store, unless someone can show me otherwise. Currently I can see the following options: 1. Before installing ML: Use internet recovery / recovery hd to install Lion onto a USB drive, just after it’s finished downloading and the screen goes blank, disconnect the USB drive. Reboot into your main partition and now you can extract InstallESD.dmg from the external drive and proceed to create a bootable Lion installer on a flash drive / dvd, as if you had downloaded the Lion install from the MAS. 2. Create a Lion recovery bootable USB stick using Apple’s tool, if you have a Lion recovery HD partition. Not as convenient as point 1 if you need to reinstall Lion more than once, since you’ll need to re-download ~4GB each time. 3. Using Internet Recovery in the EFI… this is the bit that I am not so sure about and I cannot/ don’t want to confirm it since I’ve ML DP running in a separate partition and I am not prepared to overwrite my Lion installation on any of my computers at this point in time. Does anyone know or have educated guesses on how this will work? We can currently use Internet Recovery to reinstall Lion. So what happens if you upgrade to ML and overwrite your Lion installation? Does the IR in the EFI get updated to only reinstall ML or can you still reinstall Lion as well? Any thoughts or tips would be greatly appreciated.