Plug-in the USB drive, wait for a while, if the drivers are not yet installed and let the system recognize the new drive. Now start the Windows command prompt and type the following commands one after the other as given below:
Now that the drive is ready for installation of the new operating system, start the GimageX utility and click on the tab ‘apply’. In the source field, specify the ‘INSTALL.WIM’ file, which you earlier extracted from the Windows ISO file. In the destination field, select the USB drive letter that you just got ready. Let all the settings in the remaining fields be untouched and hit the ‘Apply’ button. GimageX will not extract the contents of the Install.wim file, which contains the necessary Windows 8 folders and system files on the USB drive. Note: This procedure should take a few minutes and will depend on the speed of your USB drive.
In the command above, g: is the drive letter of the USB drive where the Windows 8 files have been extracted to earlier by the GimageX utility. Remember to replace the drive letter of your USB drive, accordingly. This command will take a few seconds to transfer the necessary booting files to the USB drive. Once done, you can quit from the command prompt.