My system has two hard drives:
sda = Windows 10
sdb = Arch and Slackware
In the "BIOS" it says "UEFI BIOS".
It is configured to boot from sdb and I am using Grub2 on an MBR disk.
My first thought was to convert Disk 0 with Windows to use GPT and then install TrueOS to data drive D:.
Then I came across this: Dual_boot_with_Windows
I think this is kind of what I was wanting to do: configure sda to use GPT and sdb to use MBR.
Use Grub2 to boot Arch or Slackware from sdb but still be able to get to Windows and TrueOS on sda.
My next guess would be to just use Grub2 on sdb to access Arch and Slackware leaving out Windows and TrueOS.
I would hopefully still be able to get to Windows and TrueOS by using the BIOS boot menu to boot from sda.
I would also need to figure out how to add TrueOS to Windows' boot loader.
If anyone knows for sure it will not work please let me know so I can stop wasting my time.
Or if you know of a way to simplify what I am trying to accomplish kindly clue me in.
I'm just trying to get my ducks in a row before I jump in.