OK, having just completed getting Windows 8.1 via Bootcamp up and running on my nMP, that was a little bit of a chore, all things considered. Things to consider that I ran into: Windows on a SATA internal hard drive will not boot from a USB Enclosure (Did not know that). I hear a Thunderbolt Enclosure might work differently? (1) The new mac pro will only allow Bootcamp installation w/Windows 8.0 or later. (I had Windows 7) (2) The new Mac Pro/Bootcamp will only allow Window installation from a USB Flash Drive. (It would not let me install from the USB DVD player and the physical Windows 8.1 DVD) (3) Do not partition your SSD prior to Bootcamp installation. Bootcamp made me undo my partition, put it back to the original and then during installation asked me to partition the SSD again, the options I saw was 20 GB or Split in Half. (I chose split it in half) (4) Buy Full Version of Windows 8.1 from Walmart $120 or wherever. I made the mistake of getting mine directly from Microsoft thinking I could simply download it. When I did download it, then it tried to update my Windows 7 on my SATA drive to Windows 8.1 which I didn't want because I would not be able to run Windows from the USB hard drive. I called Microsoft back, explained the situation and Microsoft told me I would have to wait for the DVD which was another $15 although I did receive both a 32 bit and 64 bit version. If I would have bought the FULL version of 8.1 from my local Walmart store it would have saved me a 5 day shipping wait and the extra $15. So: (1) I had to partition part of my nMP SSD to allow installation of Windows 8.1 (since the USB hard drive does not work for Windows) WAIT for BOOTCAMP to Partition the SSD!! (2) I had to purchase a FULL version of Windows 8.1 $120 (I had Windows 7) (3) You will need a USB DVD player to play the DVD to create an .iso image of the Windows 8.1 (I already had a USB DVD player) (4) Then I used Applications/Utilities/Disk Utility (The Disk Utility program) and my Windows 8.1 DVD showing up in the Disk Utility program. In Disk Utility, I selected the Windows 8.1 DVD and then I selected New Image+. In the drop down window under Image Format, I selected DVD/CD Master w/Encryption set to None and saved that to my Desktop. This takes a little while to create the file but when I was completed I had a .cdr file. Simply click on the name and change the .cdr to .iso. Now you have an .iso file of the FULL version of Windows 8.1. (5) Insert a BLANK USB Flash Drive (or save all data on it to your SSD) in a USB port on your nMP. Otherwise the installation process will erase anything that is on that USB drive. (6) Launch the Boot Camp Assistant program found in Applications/Utilitites/Boot Camp Assistant. Hit Continue and CHECK Create a Windows 8 or later install disk and CHECK Download the latest Windows support software from Apple. Hit Continue again. Select the .iso file and Bootcamp will now create a WININSTALL on the USB Flash Drive. The Windows 8.1 ISO file is 4.43 GB in size so you will need a flash drive larger than that. (7) As I recall, it was here where Boot Camp wanted to partition the SSD and I proceeded as noted above selecting Split in Half. After that I ended up with a screen showing my OSX partition and the Windows partition that was named BOOTCAMP. I selected the BOOTCAMP partition but could not proceed until I formatted the BOOTCAMP partition as MS-DOT (FAT). After that, everything was pretty straight forward and the installation of Windows 8.1 proceeded normally (took 30 to 45 mins. as I recall). Remember to have your Windows 8.1 Product Key available because Windows 8.1 asks for that immediately. At the end, the Bootcamp program completed installation on Windows 8.1 to allow for booting back to OSX. There may be some shortcuts to this that I missed. Hopefully, this helps someone. Please add any additional info that I missed or any shortcuts. This is how I did it. If there are better ways, sorry, this is how I muddled my way through it.