How to Create a Portable Windows USB Flash Drive

It is possible to create a portable bootable Windows 7, Windows 8, Windows 8.1 and Windows 10 USB flash drive, containing all your software without requiring Windows To Go.

Windows To Go is a feature in Windows 8 Enterprise, Windows 8.1 Enterprise, Windows 10 Enterprise and Windows 10 Education that allows them to boot and run from certain USB mass storage devices such as USB flash drives and external hard disk drives which have been certified by Microsoft as compatible.

You will need a spare license for the copy of Windows you install on the USB flash drive, but it has the advantage of being able to let you view all the folders and files on the host PC.

To create a portable Windows installation you will need an Windows install DVD or ISO file.

1. Open the Command Prompt by typing cmd.exe into Start Screen or Start Menu, right-click on Cmd.exe, and open it as an administrator.

2. Type diskpart and press Enter key.

3. Type list disk and press Enter key. This displays a list of disks in your PC. Make a note of the number for the USB flash drive (1, 2, etc.).

4. Type select disk n, where n represents the disk number for your USB flash drive.

5. Type clean and press Enter key to prepare the drive for formatting.

6. Type create partition primary and press Enter key.

7. Type format fs=ntfs quick and press Enter key.

8. Type active and press Enter key to make the newly created partition the active (bootable) partition.

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9. Type assign letter=u and press Enter key, to temporarily assign a drive letter to the flash drive so you can install Windows onto it.

10. Type Exit and press Enter key to exit Diskpart.

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11. Now place your Windows installation DVD into your DVD drive or mount your ISO image as a drive. You can mount ISO images natively in Windows 8, Windows 8.1 and Windows 10 by right-clicking them and selecting Mount from the options that appear. In Windows 7 you will need a third-party utility such as WinISO.

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12. Back at the Command Prompt type dism /apply-image /imagefile=f:\sources\install.wim /index:1 /applydir:u:\ where f: is the location of your ISO file or DVD and u: is the USB flash drive. This will copy the Windows installer image to the flash drive and takes around 8GB of space, i recommend size of the USB Flash Drive to be at least 30GB. When you download a Windows 10 or 8 ISO file, by using the Media Creation tool, you will realize that there is an "install.esd" file under the "sources" folder (X:\Source\install.esd). If you have install.esd file instead of install.wim file in Source folder then execute dism /apply-image /imagefile=f:\sources\install.esd /index:1 /applydir:u:\ command.

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13. Type bcdboot u:\Windows /s u: /f ALL and press Enter key, to set the USB flash drive as being bootable.

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You can now boot your PC from the flash drive, but note that you may need to change the boot order setting in the BIOS/UEFI.

The initial setup process for the flash drive when you first start the PC from it can take some time, and it’s a good idea to do this on the PC you intend to repair, as moving the drive between different PCs especially with different BIOS/UEFI types can result in the flash drive not working on some machines or Windows believing the hardware it has been installed on has changed, and asking for a fresh product key.