Q: Boot Camp says "We couldn't create a new partition or locate an existing one"

I'm trying to install Windows 8.1 using Boot Camp, after previously deleting my Windows 10 partition after getting into an Auto Repair loop. I get the following error after hitting the "format" button on Windows Setup: "We couldn't create a new partition of locate an existing one. For more information, see the Setup log files."

From looking at other pages, I'm noting that I seem to have more drive partitions than others do (although Disk Utility says I only have no partitioned discs). In the Windows Setup screen, the following things are shown:

Drive 0 Partition 3                         128.0MB          0.0MB      Primary    

Drive 1 Partition 1:EFI                    200.0MB     196.0MB     System    

Drive 1 Partition 2                         412.1GB          0.0MB     Primary

Drive 1 Partition 3                         619.0MB          0.0MB     Primary

Drive 1 Partition 4:BOOTCAMP     518.6GB          518.5GB Primary

Why does it seem I have so many partitions? Disk Utility only shows I have one (plus the Boot Camp one). Is this preventing me from installing Windows 8.1? I used BootCamp when my computer was new, 2 years ago, and had no problem at all. And I've added no partitions since (to my knowledge).

Any assistance would be greatly appreciated!