This is my current partitioning scheme since adding a third drive to the system (WD Blue 500GB). Running Windows 7 alone on the SSD and two different Linux systems on each of the two mechanical hard drives. The first Linux sys on each drive has it’s bootloader installed on the MBR of that drive. The second Linux sys on each drive has it’s bootloader installed on the root partition of that system. When a new kernel is updated on any Linux system, the bootloader of each MBR-installed system is updated (sudo update-grub) so they will re-detect the changes. I use the motherboard’s boot menu to access either of the mechanical hard drives’ grub boot menu from which I can boot into any of the five operating systems… or I can let the computer boot to the SSD and Win7 as default with no interaction of the motherboard boot menu.