<Sort of solved> "Unable to find a medium containing a live file system"

[gold_finger]

I'm about as stumped as you unfortunately.  Don't see anything in specs to indicate you should be having problems.  Looks like you've got Mint 18 Mate on that computer now, not 17.3, but that doesn't matter.  You got it installed before, so makes no sense that nothing works now.  Very strange!


Computer just using open source AMD driver for graphics in Mint Mate 18 and I'm assuming everything works fine with it, correct?  So graphics doesn't appear to be cause of problem either.


Don't see anything wrong with current UEFI/Bios settings.


Grasping at straws now.  Don't know exact procedure you've been following to boot the USBs, but if you've just been relying on boot order setting in main UEFI Settings Menu (accessed through <F2> key during startup), maybe try booting with the per-session Boot Menu instead.  Looked-up info on your computer.  Appears you can invoke per-session boot menu with the <F12> key, then choose USB there.  Another method is to use the "Novo" button, then choose "Boot Menu" and pick USB there.



If still no luck, maybe look on Lenovo site for UEFI/Bios update.  Maybe there is some kind of glitch in old one on machine now (Bios: LENOVO v: A1CN24WW(V1.12) date: 10/17/2014).