[Linux Mint] Issues With Boot Repair: Not detecting bios_grub partition

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http://ubuntuforums.org – So, I'm dual booting linux for the first time on my computer. I run Windows 8 native on an unpartitioned 500gb internal HD. I want to install Linux Mint 13 Cinnamon 64bit to a partition on my 3TB External HD. I have made a live USB thumbdrive and gone through install, then rebooted into linux via the thumbdrive in order to enable Grub per these instructions. I ran Boot Repair but got an error code. I made a new unformatted 6mb partition and flagged it as bios_grub as per the error code when I attempted to run boot repair, but boot repair kept giving me the same error. I did step 10 and runnin (Hardware)