How to write a Windows installer to USB flash drive from .iso
This will erase the flash drive. Data loss will occur if
there's anything important on the drive before you start.
Not recommended for Apple Macs, and might not even work. Please refer
documentation on installing Windows on a Mac instead.
Microsoft has also published this procedure on its blog.
The blog post predates this article.
When you want to install a fresh Windows on a computer without an
optical drive when you have nothing but an .iso file, you might find
yourself a bit challenged.
This article describes how you can format a flash drive on another
Windows computer, so that it will boot the Windows installer. You can
then use this flash drive to install a fresh copy of Windows. This
method is known to work for all Windows versions from
Windows Vista up to Windows 10,
including server versions.
Formatting the flash drive
First, you must format the flash drive. Follow these instructions on a
Windows machine with the flash drive inserted.
You need a Command Prompt with administrator
privileges. In the Start/Metro
-menu, type cmd. Rightclick cmd and
click Run as Administrator. Now, run
diskpart. Diskpart will re-partition and format the drive,
and install Microsoft bootcode in the MBR. During this process, you
will get a list of all disks that are available on the machine. Take
note of the
number in the output
list disk that corresponds to your flash drive, and use
it in the
select disk command.
Execution of diskpart
Microsoft DiskPart version 10.0.10240
Copyright (C) 1999-2013 Microsoft Corporation.
On computer: DISKPART-DEMO
Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 40 GB 0 B *
Disk 1 Online 7651 MB 0 B
number is now the selected disk.
DiskPart succeeded in cleaning the disk.
create partition primary
DiskPart succeeded in creating the specified partition.
select partition 1
Partition 1 is now the selected partition.
DiskPart marked the current partition as active.
format fs=ntfs quick label="
100 percent completed
DiskPart successfully formatted the volume.
Copying the Windows installation files
Simply mount the .iso, and copy all files to the freshly formatted
flash drive. If you are on Windows 8 or newer, this
can simply be done by double-clicking the .iso. On
Windows 7 and older, you need some third party
software, like WinRAR.
Now it's time to take the flash drive and put it in the computer where
you want to install Windows. Make sure your EFI/BIOS boots from USB
(often this can be done by pressing F11 or F8
during boot). Install Windows as you would normally do.