Yippie. I figured it out! It turned out that the problem was that I needed to convert the HDDs to MBR disks, or Master Boot Record disks.
Before converting them, the two HDDs were GPT disks, or GUID Partition Table disks. I suspect this is because they both came out of computers that used UEFI instead of a traditional BIOS, and GPT disks are read differently when connected via USB cable vs an SATA cable to the system board. Once I converted them both to MBR disks, which I did by right clicking on the part that says Disk 2 and clicking "Convert to MBR Disk", the partitions created like they normally do, with the first three being primary partitions and the fourth being an extended partition with multiple logical drives. :)
