I've just put a new SSD in my X220 and what ever I do it won't boot. I've tried both Grub2 and SysLinux, UEFI and legacy BIOS. I am using a USB drive to start Grub2 and then boot on to the drive. The SSD is using GPT, could that be the problem?
i) The X220 will not boot using legacy BIOS from a GPT disk.
ii) You have to have the file /boot/efi/efi/boot/bootx64.efi for the machine to boot without "signing" it into the UEFI menu.
Also note that the BIOS option disabling UEFI USB booting disables *all* USB booting.