MacOS – How to use OSX to create a bootable USB key to install Windows 8.1 on a PC

This adds on to Django's answer, pointing out how to allow the option for revealing "Create a Windows 7 Installation Disk" in Boot Camp Assistant.

I checked the Bootcamp documentation and it says I may have the option to "create a windows installation disk" but I don't have that option (unsure why?)

Because you cannot see this option, it is most likely because your computer is not supported in Boot Camp Assistant.app's Info.plist. However, that can be quickly changed.

1. Open a new Terminal window and run sudo nano /Applications/Utilities/Boot\ Camp\ Assistant.app/Contents/Info.plist

2. Type in your password.

3. Move with the arrow keys down to the bottom where it says:

(I meant to start with " (<) key (>) USBBootSupportedModels (<) /key (/>), but I don't know how to ignore HTML markup here. _{If a moderator or someone who knew how could change this, that would be great.}

<array>
<string>IM130</string>
<string>MM50</string>
<string>MP60</string>
<string>MB80</string>
<string>MBP90</string>
<string>MBA40</string>
</array>

Check for your computer model number in  > About this Mac... > More info... > System Report... in Hardware Overview under Model Identifier. It should be something like

    Model Identifier: iMac10,1

iMac = IM, Mac mini = MM...and your MacBook Air would be MBA. Now, simply take MBA and add it to the numbers after (MacBook Air3,2 to MBA32) without the comma.

Go back to your Terminal prompt and remove the current string part with MBA (you may want to make a note of this somewhere, in case you decide to revert later). Replace it with an identical one that says:

... <string>MBA32</string> ...

(Without the ellipses)

Now save the file by typing Control-O and confirming the WriteOut by pressing the return key (make sure Wrote xx lines appears). Quit and re-open Boot Camp Assistant, and the option should be available!

At this point, you can select your .iso image, as usual (given that you've already converted the .img)

I am not really sure why you would want to install Windows 8.1 without BootCamp.

The USB stick needs to be a little bigger than the .iso file you are going to be burning. It doesn't matter if there is any data on it, this will totally erase the whole thing.

Steps To Achieve Victory

1. Download the ISO you want to use

2. Open Terminal (in /Applications/Utilities)

   2.1 Navigate to the path where the .iso file is located

   2.2 Use ls to list all the folders

   2.3 cd /path/to/iso to dive in to folder or cd .. to go back the path

3. Convert .iso to .img using hdiutil:
   hdiutil convert -format UDRW -o /path/to/target.img /path/to/source.iso
4. Rename if OS X gave it a .dmg ending:
   mv /path/to/target.img.dmg path/to/target.img
5. Type diskutil list to get a list of currently connected devices
6. Insert USB drive you want to use
7. Run diskutil list again to see what your USB stick gets assigned eg - /dev/disk3
8. Run diskutil unmountDisk /dev/diskN (where N is the number assigned to your USB stick, in previous example it would be 3)
9. Run sudo dd if=/path/to/target.img of=/dev/diskN bs=1m (if you get an error, replace bs=1m with bs=1M
10. Run diskutil eject /dev/diskN and remove your USB stick
11. The USB stick will now be ready to use

IMPORTANT For the step #9 you can use the destination to /dev/rdiskN to reduce the copy time.

NOTE: Sometimes, not always, Step #4 will be necessary. Not all the time. I am not sure why it will add the .dmg ending and other times leave it alone.

NOTE 2: Might I suggest you learn the name of the .iso you downloaded, or just rename it win8.1.iso or something, and put it on your Desktop folder. That way, when you are typing commands like #3 and #4 etc, etc, you can type it like this:

hdiutil convert -format UDRW -o ~/Desktop/win8.1.img ~/Desktop/win8.1.iso

and

mv ~/Desktop/win8.1.img.dmg ~/Desktop/win8.1.img

and step #9 would look like this:

sudo dd if=~/Desktop/win8.1.img of=/dev/diskN bs=1m

IMPORTANT - You can track the progress by pressing CTRL + T It will show the process info and records in and out, since we use the bs=1m each record is 1Mb in size so you can easily track the progress.

I don't mean to be insulting with Note and Note2, I am just making sure that you know what all these commands mean. It's the simplest method. Unless someone else comes up with something better.