BIOS won't recognize hard drive with Ubuntu installed

Sep 4, 2018
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Bit of an odd question here! Absolutely no idea what's going on, so I'm open for any answers.

I have two installed hard drives - a 240GB SSD, and a 1TB WD Blue HDD. I have my main install on the SSD, and a file partition and an ubuntu partition both on the 1TB HDD. I installed Ubuntu to the 2nd partition, made sure to install GRUB to the 2nd drive and everything, yet when I entered the BIOS to configure boot options, only the SSD appeared, no HDD. Tried a reinstall, with no avail. I'd prefer not to wipe the HDD if possible, but I can work something out if it comes to that. Any ideas on what I'm doing wrong?

Motherboard: MSI A320M
SSD: 240GB PNY
HDD: 1TB WD Blue SATA 6gb/s 7200rpm

Thanks!