Using Windows 8 .img file to create a bootable USB thumb drive

Question

Is it possible to create a bootable USB drive for installing Windows 8 without access to a copy of Windows?

I know I could install a VM and install Windows there, then make the bootable drive and use Bootcamp to actually install that way, but honestly I would rather not have to put the extra software on my system if at all possible.

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?)

Additional information: USB Key capacity: 1 16gb and 1 30gb OS ver: OSX Mountain Lion Machine: Late 2010 MacBook Air

Answer 1

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)

Answer 2

It seems Bootcamp Assistant should be able to help you with this (especially as you have a MacBook Air). It odd that it doesn't. Another weird move from Apple. Because of this you may need to do some system editing, as ethanlee16 points out, to convince BA to give you the option of creating a Bootable USB.

Follow his instructions, or if you don't want to go into terminal, follow these instructions.

And then follow these:

First, convert your Windows 8 .img file to an .iso file. You can do this within OSX by following these simple instructions.

Next, just use the new .iso image with Bootcamp Assistant to create a bootable USB drive with Windows 8 on it. These instructions (as posted by Alexandr Mazanov in the comments) do a great job of explaining what to do.

No need for Windows or any VMWare. Good luck!