Folks, this is what i've been trying for the last few days.
The result is the same. Files are all there on the USB, i tell the laptop to boot from it and all is get the nice colorful introductory screen.
Otherwise, on normal boot i get: "error no such partition grub rescue>"
My hunch is Windows MBR was mixed in with the Linux when i tried to awkwardly uninstall LinuxMint.