Hi, I just wanted to put a few words down to possibly help people who are having issues with BootCamp, as I was. When I first got my 2014 riMac, with stock RAM, and 3TB Fusion Drive. It came preinstalled with Yosemite, and before I even installed additional RAM, I used BootCamp to install Windows 8. Worked without an issue. However, somehow Windows got "corrupted," and would only boot properly about 1 in 4 times. This was after almost a year of light use. I had installed updates to Mac OS since then, as El Cap came out in the interim. I tried to reinstall Windows, tried WinClone, etc., all without success. Always got hung up on the partition issue, and Windows would NOT install, saying it couldn't create the partition. Either that, or the format was incorrect. I tried everything imaginable to get it installed, without success. Also, in using other, sometimes non-Bootcamp methods to try to get Windows installed, I would end up with "ghost partitions" on my Fusion Drive (3 TB). These would be impossible to delete, and in the various attempts, I would sometimes end up with an un-fused Fusion drive. This would complicate things immensely. I tried wiping out both Mac OS, and Windows, reformatting the drive, rolling back to Yosemite (hey, it worked initially!) all without success. Always, BootCamp would properly format the drive, and the computer would restart, and would never get past the initial install screens in Windows. I gave up for a couple years, and then tried VMWare Fusion, and Parallels. I really didn't like either of them, and they suffered for speed, especially with Steam games. I thought I'd try again this past week. I backed up using TimeMachine, and then tried BootCamp. No luck-same thing. I had read about (and already had tried multiple times) unplugging everything including anything USB other than the Windows USB install key. Same thing-would not be able to create a formatted partition that would allow Windows to be installed. I tried removing the RAM I'd added. Same thing. What did work, finally, was multiple PRAM resets, unplugging the computer, waiting a minute, then doing a complete re-format, install of Sierra, and then immediately doing a BootCamp install. This time, it was able to complete the process. No "ghost partitions," and a proper install that updates. Lessons learned- 1. I will never get another Fusion drive. It works fine in Mac OS, but Windows doesn't seem to play well with it, and although I finally got it installed, the fact that Windows would un-fuse the Fusion drive without warning was enough for me to question the overall stability. You may find otherwise, but I'll not get another Fusion drive, and would have opted for the 1TB SSD in retrospect. 2. Windows installation is finicky on my 2014 riMac, and it's best for me to not mod it at all, keep it simple, and refrain from anything that may corrupt the boot process. 3. Sierra/El Cap seem to lack the function in Disk Utility to re-fuse a Fusion Drive. The way I finally got that done was to use Terminal to create a LVG, and then Yosemite (via Recovery boot) to format it properly. 4. Keep latest OS installs on hand on USB keys-this slowed me down, as I only had 1 4GB key handy-not enough for the MacOS USB key, although it would simply error, not tell me the size was insufficient. 5. Back it up. I do back up to a RAID, and that, though better than a non-RAID backup system, can be some false security. If the hardware goes wrong, in many cases, you're out of luck, even if the disks themselves are fine. I learned this the hard way, and now backup to 2 different systems. It was a very frustrating year or two, because whenever I tried to install Windows via BootCamp, I would often end up with a fragmented/ghost partitioned drive, that would be a hassle to fix. However, with the PRAM reset, unplugging, and no external devices installed, it finally, finally worked for me. Good luck!