Recently, I purchased a used Mid-2012 Non-Retina MacBook Pro. I replaced the optical drive with a bay for the original HDD and put an SSD in where the HDD used to be. I have a fresh installation of macOS 10.13.3 High Sierra on the SSD, and nothing but an EFI boot partition for Windows 10 on the original HDD. When I boot into the Windows 10 installer, made with Boot Camp, everything works fine until I format the Boot Camp partition, where it tells me that, "Windows can't be installed on drive 1 partition 2." When I look at the details it tells me, "Windows cannot be installed to this disk. The selected disk is of the GPT partition style." and "Windows cannot be installed to this disk. This computer's hardware may not support booting to this disk. Ensure that the disk's controller is enabled in the computer's BIOS menu." This occurred when i initially booted into the Boot Camp installer, and whenever I boot into "Windows" from the boot menu from the flash drive. Whenever I boot from "EFI Boot" from the flash drive, it lets me click "Next" but gives me the error, "We couldn't create a new partition or locate an existing one. For more information, see the Setup log files." When I hit "Next" with the partition deleted and selecting its unallocated space, it starts installing but gives me the error, "Windows could not prepare the computer to boot into the next phase of installation. To install Windows, restart the installation." I would like to install Windows 10 on the hard drive, and not on the SSD with macOS because the SSD is already only 128 GB, and I don't want that getting any smaller. Any help would be appreciated!