Note: Due to bandwidth limitations I approached the install of Windows 10 manually, completely bypassing the Boot Camp Assistant.

In order to install Windows 10 on a Mac you either need a secondary internal drive or a second partition on your primary internal drive. Since I had a 1 TB internal drive, I decided to create a second partition on the primary drive.

I did this by launching the Disk Utility and, while having the primary internal drive selected, clicked the Partition tab. I was greeted by an interface displaying the Partition Layout with just my Macintosh HD partition listed. I added an additional partition, filling in the Name and Format fields as I wanted to new partition to be seen. The partition did not matter at this point, so I chose something Windows would recognize: ExFat. I then moved the slider between the two partitions until I found the balance that I wanted.

It should be noted here, if you run into any complications and have to change the size of your new partition, you will run into errors. The primary partition cannot be adjusted while in use — this includes booting into the Recovery Partition. In order to reconfigure any partition size you will have to boot from an USB installer of OS X. You either have to get it right the first time or create a USB installer of OS X before you begin. I ran into this issue when I did not realize I had to drag the slider in the middle to adjust the sizes of the partition and just typed it in the Size field instead, which did nothing.

After I had the additional partition created I rebooted the system. I held the Option key to select from which drive I wanted to boot and was presented with all of the different options. Since I already had an ISO of Windows 10 burned to a DVD, I booted from the Windows Installer DVD.

I was immediately presented with the Windows 10 setup screen, but to begin the setup process I had to find a USB mouse. The required drivers for the Bluetooth mouse that came with my iMac were not included in the Windows 10 installer package. During the setup I had to reformat the newly created ExFat partition to NTFS, because Windows 10 will not install on FAT or ExFat. This only took a few seconds, as it was a quick format.

After configuring the installation just as I wanted it the installer ran through the rest of the install process, the computer rebooted and presented me with the OS X desktop. It is then that I remembered OS X was set as my default boot destination. This was fine for me, as my wife uses the computer often and would not want to have to pick an environment to boot the computer into each time she has to restart the iMac.