Triple Boot

Hi folks,

After treating myself to a 500GB Samsung SSD and installing it with the helpful advice from the folks at OWC, I'm trying to set up a triple boot set up but keep running into problems.

I have a mid 2010 27" iMac (shipped with Snow Leopard), I have done a fresh install of macOS Sierra and wish to add Windows 8.1 and Linux (Elementary OS) and round it of with installing ReFind.

I have gone through the Bootcamp procedure with my Windows DVD in the SuperDrive and the SSD partition process goes smoothly but when after reboot trying to select the partition to install Windows I get the "partition is of the GPT type". I have installed GDISK and changed the partition setup from Hybrid to Protective MBR but still get issues. I have also disabled the system protection as well.

Can anyone advise where I'm going wrong or advise best plan of attack?

Thanks in advance

Can I ask why you are trying to triple boot? Also, you should really be on Windows 10, not 8.1. You might be better of just using a virtual machine through free software like VirtualBox to run the other OS'..

I have applications that I use in all 3 OSs, and I only have a licensed copy of Windows 8.1. Is it better that I install El Capitan rather than Sierra for Triple boot with Win8.1? I'm not a fan of virtualisation products due to the applications that I run.