Hello I was trying to update the operating system on my 2013 iMac from the Maverick 10.9 to the newer OS 10.11 and my computer kind of froze up! So I inserted the START ME STICK I recently bought into my 2013 iMac and tried to start up the computer from the START ME STICK. The error message I get was- "Unable to find a medium containing a live file system." What should I do? Sincerely, Dale Rogers