Creating a Windows 8.1 To Go USB installation in 5 steps!

This guide will assist you in creating a portable OS (Windows 8 To Go) on a USB thumb drive/device.

NOTE: This guide assumes you have an understanding of basic IT terminology such as USB, NTFS, SSD, ISO, etc.

Stuff you need:

1. 16G (or higher) USB storage device. This can be an USB thumb drive or an USB 2.0 (or higher) external hard drive with say a SSD drive like mine :) (MUCH quicker than the thumb drive!).
2. Windows 7 PC (Laptop is fine). You can use Windows 8 too (can mount ISO's without third party software).
3. The 'install.wim' file from the Windows 8 DVD or ISO. If you only have the ISO, make sure you have a tool such as UltraISO or WinISO. These tools will allow you to mount the Windows 8 ISO file to copy the 'install.wim' file (located under \sources folder) locally to your Windows 7 PC (e.g. C:\Temp\install.wim).
4. The 'ImageX.exe' executable file from Windows 7 Automated Installation Kit. The only file you need from the Windows 7 AIK is 'imagex.exe', so if you can find this alone somewhere else, go ahead and just download that particular file. To minimise confusion, place imagex.exe with the 'install.wim' file.
5. Check that your BIOS is configured to boot off USB devices or has the capability during POST to select what device to boot from.

The Process:

1. Insert your USB device and format the drive using NTFS file format. Under Computer Management>Disk Management, check that your USB device is set to active, contains one primary partition and has a letter assigned to it (lets just say its F: for this tutorial). Alternatively you can run the following diskpart commands (type the following in a command prompt:    Diskpart
   List disk
   Select disk n (where n is the number that was given for your stick in List disk)
   Clean
   Create partition primary
   Format fs=ntfs quick
   Assign
   Active
   Exit 
2. Insert DVD or mount the Windows 8 DVD/ISO. Copy install.wim to a temporary location on your PC (e.g. C:\Temp\install.wim)
3. Launch cmd.exe (using administrative privileges) and change to the directory that 'imagex.exe' and 'install.wim' are located.
4. Type in the following (without quotation marks) 'imagex.exe /apply install.wim 1 f:\'
   Depending on your hardware, this can take anywhere from 10mins to 60mins.
5. Once the wim file has successfully deployed, run the following (again, without quotation marks) 'bcdboot.exe f:\windows /s f: /f all'
   This will create a boot files on your USB.
6. Reboot your PC and enjoy!

I've tested Windows 8 To Go on a Dell E4310 and the latest (currently November 2012) Apple MacBook Air (13 inch) without any issues. Both laptops work very smoothly, albeit, this is probably due to the 64Gb Kingston SSD I have in my USB 2.0 Vantec HD caddie.