Welcome, Andrew Crain!
What is the model of your motherboard? Also what is the operating system that you are using?
I'd suggest you to try to resolve this by resetting BIOS using one of the methods listed in this tutorial:
http://www.wikihow.com/Reset-Your-BIOS
Keep in mind that this will get your BIOS settings back to factory defaults, so you'd need to re-configure them again after the reset.
I'd also check for any firmware updates on your motherboard's website, the 5 TB HDD might need an updated BIOS.
However, keep in mind that in order to use greater than 2 TB HDDs on your system your OS will need to be a 64-bit version, because they have the capability to use the GPT (GUID partition table) which can partition both internal and external HDDs far beyond the 2 TB limit that comes with the MBR partition table.
Keep me posted!
SuperSoph_WD