Note The version of Windows PowerShell 3.0 for Windows 7 does not contain the Storage module at this time, so Windows 8 or Windows Server 2012 is a requirement. It vastly simplifies things and, not only that, it contains help, too.
Here is my version with it all put together. You can download the complete script from the script repository. Now the entire process can be scripted with all Microsoft tools.
Wait, there’s more! The storage module has a Mount-DiskImage cmdlet.
Use Copy-Item to copy your install bits to the USB drive and you’re done.
Summary: Microsoft PFE Jason Walker talks about creating a Windows PowerShell script to create a bootable USB drive.