Boot confusion

[Ralf Mardorf]

Just use the SSD with an MBR.

Note, you can install grub to all of your drives, but only grub of the
disk is used, that the BIOS/UEFI setup mentions as the top drive of
those drives. There's also no need to disable any drives, to ensure
grub is installed to a wanted drive.

Almost all instructions available by the Internet should work, e.g. read

  https://help.ubuntu.com/community/Grub2/Installing#Reinstalling_GRUB_2

just the part

  "Fixing a Broken System" > "via the LiveCD terminal"

Feel free to use a LiveDVD or LiveUSB terminal ;).