(Article disponible en français à cette adresse : https://onefor4.wordpress.com/2011/09/05/crez-une-cl-usb-bootable-pour-installer-windows-7/ )
From graphical user interface
Nowadays, when you buy a new laptop, you may have no DVD drive. In this case, if you want to install Windows 8 or Windows 7, you will not be able to burn a DVD and install the system from it.
Fortunately, quite all motherboards allow us to boot from an USB key. We will use it to launch the Windows 8 setup. First, we have to get the iso file used to the system set up. MSDN subscribers can download it legally. For the others, if you have bought the DVD, you can create an iso file from a computer with a DVD drive, softwares like poweriso or deamon tools lite will create it for you.
Once you have your iso file, you have to put it on the USB key but not from a simple copy/paste. Some additional operations are needed. Microsoft have created a freeware to create bootable USB keys for Windows 7, Windows 7 USB/DVD Download Tools, you can download it on the Microsoft Store.
You just have to launch the software, select the iso, your usb key and start the copy. Once all these operations ended, the USB key is ready, you can launch the install.
But sometimes, with some iso files (especially from MSDN), the copy fails and you obtain the following error “We were unable to copy your files. Please check your USB device and the selected ISO file and try again” while your iso have been checked and so your usb key.
In this case, we will have to use the command line interface.
By the command line interface
The first step is easy : plug your usb key Then, download an utility to create virtual dvd drives like poweriso or deamon tools lite. If you are running the Windows 8 Release Preview, you will not need another software, Windows 8 do it for you. Finally, mount the iso and check the letter assigned to your virtual drive (here F: ).
Format the USB key with Diskpart
The following step consists in create a primary active partition on the key and format it in NTFS. For that, we use the CLI utility diskpart. In Windows 7, launch the CLI in administrator mode by clicking “start”, “all programs”, “accessories”, right click on “Command prompt” and “launch as administrator”. On windows 8, type “command line” on the start menu, right click on “command prompt” and “launch as administrator”. Now, type:
The command line now switches to the disk management utility named “diskpart”. List all available disks with:
You can see that my USB key is “disk 2” (obviously, not the 931 GB drive ). To create the partition and format it in NTFS:
select disk 2 (replace the number corresponding to your usb key)
create partition primary
select partition 1
format fs=ntfs (formatting can last several minutes)
assign (a letter is assigned to your usb key, maybe different from the letter assigned in the beginning)
Create the boot sector of your usb key with bootsect
After “exit”, you are again on the starting CLI. Open “computer” to know the letter assigned to your usb key (here G: ). You will first set on the “boot” folder on the virtual Windows 8 DVD :
F: cd boot (replace F: by the letter corresponding to your virtual dvd drive)
Then a last command will allow booting on your usb key
bootsect.exe /nt60 g: (replace G by your usb key letter)
And to finish, simply copy/paste all files from your DVD to your USB key and set your BIOS to check USB boot before hard drive boot.
Happy installation, and enjoy Windows