The disk boot mode is currently set to AHCI because if I set it to IDE or RAID, I get a BSOD. In AHCI mode, Windows boots fine and everything works, but unfortunately, I can't see the HDD in BIOS or Windows. The drives are currently occupying the SATA3 0 and 1 ports on the PC, but I've tried multiple ports and the HDD still doesn't appear.
What's funny is everything was working perfectly until I cleared the CMOS (long story but it had to be done). I had thought that the Boot Mode was the only thing that needed to be changed, but there must be another setting in BIOS that needs to be changed too. Just don't know what it is.
More about :hdd recognized bios win7 ahci mode culprit
Go into the system BIOS and check to see if there is a section that allows you to enable and disable drives (not the same as selecting primary boot drive). It is possible that when you reset the CMOS that BIOS settings might have changed back to default. I am not familiar with your motherboard or your specific BIOS so I don't know if this is an option available to you. I've run into several builds where I had to enable drives in the BIOS but they weren't Gigabyte motherboards.
BTW - Have you tried a different SATA data cable and a different power cable with your hard drive?