Other operating systems can boot from external USB or FireWire drives, but Windows has, to my knowledge, never had this ability, at least not officially out of the box.

How is it with Windows 7? Can it be installed to and booted from an external drive?


I have spent a few days looking around for a solution to this and also made an attempt to install Windows 7 on an external drive myself.

Long story short, the answer can be rounded down to "No, it is not possible to run Windows 7 from an external USB or FireWire drive".

The rounding error is a few guides employing hacks and workarounds and third-party tools with partial success.

Edit: Links to sites on the topic

Raymond Chen saying it isn't possible

Tom's hardware guide, 14-step process using BartPE and other tools

Another site using VMWare and a registry hack

  • 1
    Could you add some more detail? links perhaps? Nov 11 '09 at 0:12

I've been looking into this for a few days, so I can save you a step here.

Installing onto a USB drive is not the problem. You can get an installed copy there via other means, but it won't help you, because:

"Windows 7 will not boot from a USB drive."

That's the official word from microsoft. Ignoring them, I have gotten it to the point where it shows some fancy logos, but then BSOD.

Apparently it is possible to bypass that, by modifying some driver files, and installing a service to keep the modified.

But just to be clear, INSTALLATION is not going to be your main problem.


I've been researching this for the last week, and, from what I can tell, Windows has to install on a "fixed" disk. USB devices show up in Drive management as a "removable" disk.

Lexar has a utility that will flip the "removable" bit on a USB device, but so far I haven't been able to use their utility to flip the bit on any USB drive. I'm out to buy a Lexar drive to test this, but as of this post the answer is still "no, you can't install Windows 7 on a USB drive". Hopefully, this afternoon's testing will prove different.


There is a hack I've used to boot Windows 7 from a FireWire drive. My PC can boot from FireWire, but I'm aware that not all PC's can.

  1. System image backup your physical machine

  2. Install Virtual Box

  3. Create a virtual machine. Don't add any hard drives to the VM

  4. Format the extrnal drive and make it bootable http://kmwoley.com/blog/?p=345

  5. Set virtual box to access the physical external drive http://www.sysprobs.com/access-physical-disk-virtualbox-desktop-virtualization-software

  6. Within the virtual box VM restore from backup. Windows sees the external drive as an internal drive. Reboot as needed for drivers etc. The key point here is that the drivers for your physical machine are maintained.

  7. Power down physical machine and remove all internal drives

  8. Boot physical machine from external drive


Update: The VirtualBox based Windows 7 installation on a USB Flash drive article I refer at the start here installs on the USB in a VirtualBox. Has this failed to work? I will appreciate comments and reason for this late down vote.

On installing to the USB.

  1. How To Install Windows 7 On USB Flash Drive
    Refers to an earlier article on How To Install Windows 7 On VirtualBox

    • CNet: Boot Windows XP from a USB flash d1rive
    • As with most cool new techniques, there are a few catches.
      For starters, not every PC is capable of booting from a USB flash drive.
    • Another catch is that not every flash drive will get the job done.
    • The flash drive's capacity is actually a limiting factor though.
      Your flash drive can't be too large or too small.
      Recommend that your flash drive be at least a minimum of 256MB in size.
      The flash drive that you use for this project can be no larger than 2GB,
      because you will have to format the flash drive using the FAT-16 file system,
      which has a 2GB limit.
      Presently, you are stuck using FAT-16 because most computers
      will not recognize a flash drive as being bootable
      if the drive is formatted with anything other than FAT-16.

Older: On booting Windows off USB.

  1. Microsoft Store: Windows 7 USB/DVD Download Tool

    When you purchase Windows 7 from Microsoft Store,
    you have the option to download an ISO file or compressed files.
    The Windows 7 USB/DVD Download tool allows you to create a copy of
    your Windows 7 ISO file on a USB flash drive or a DVD.
    To create a bootable DVD or USB flash drive,
    download the ISO file and then run the Windows 7 USB/DVD Download tool.
    Once this is done, you can install Windows 7 directly from the USB flash drive or DVD.

    • Microsoft offers USB-bootable Windows 7 for netbooks

      Microsoft has kept netbook and other optical drive-less PC owners in mind with a new downloadable version of its just-released Windows 7 operating system. While downloads of Windows 7 were expected to arrive, the netbook-oriented versions are unique as the OS can be downloaded in a form that will boot from a USB drive instead of requiring a DVD. The downloadable OS is only available through the Microsoft Store.

    • Creating Bootable Vista / Windows 7 USB Flash Drive

      It surprised me to find that there are very few dead-simple guides
      to creating a bootable USB thumb/pen/flash drive for a Vista and/or Windows 7 installation.
      I cobbled together the following from VistaPCGuy and
      another source I don’t remember right now.

  • 2
    Points 1,2,3 are to put in the installation files of Windows 7 on a USB drive, not to run Windows 7 from the USB drive.
    – Snark
    Oct 29 '09 at 12:34
  • 1
    According to the OP, Windows has never had the ability to boot off USB drives.
    – nik
    Oct 29 '09 at 12:39
  • 2
    nice work, but i really think we're dealing with the question whether windows 7 can be used as a Live OS from a pen drive. oh, and you forgot WinToFlash.
    – Molly7244
    Oct 29 '09 at 12:44
  • @Molly, I got a bit carried away on that "can't boot Windows off USB" part :-)
    – nik
    Oct 29 '09 at 12:46
  • So is the consensus so far that this can't be done without something like VirtualBox? Oct 29 '09 at 12:53

I can confirm that it's possible: I did it over the weekend.

It takes around 30 minutes, but done from CMD. One needs to log-in diskpart to do that, clean the disk, format. You would require a Windows .iso file, and a virtual disk to transfer the image from C: to the removable drive.

  • 4
    Would be really great if you could post the instructions here!
    – slhck
    Nov 14 '11 at 16:19
  • 1
    I'm pretty sure you mean booting the Windows installer from an external USB disk in order to install it to an internal disk, rather than booting and running Windows itself from an external disk (possibly without any internal disk). Apr 5 '12 at 15:33

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