How To Install Windows 7 To USB External Hard Drive [Must Read]

As you likely know, while one can install Windows 7 from an external hard drive, one can’t install the same to an external hard drive with default settings. For all those users waiting for a good workaround to install Vista, Windows 7 and Windows Server 2008 R2 to an external hard drive, here is the complete solution.

Windows 7 SP1

Even though Windows recognizes and displays the USB hard drive in the installation screen, it doesn’t allow you install Windows on the same. When you attempt to install Windows 7 on external drive, you get “Windows cannot be installed to this disk” error.

Install Windows 7 to an USB external hard drive

So, if you want to install Windows 7 on an external hard drive you need to follow the steps given below. The procedure is simple but you need to install Windows Automated Installation Kit (WAIK) first to get some files. We would like to thank fujianabc @ boot-land forum for this workaround.


# An external hard drive formatted with NTFS

# Windows 7 installation files (if you have Windows 7 ISO use Virtual Clone Drive freeware to mount it)

# Windows Automated Installation Kit (free download from Microsoft)

NOTE: Make sure that you have a minimum of 15 GB free space on your external hard drive before starting the procedure. Although we are not going to delete the contents of external hard drive, we recommend backing up your external hard drive contents before trying this guide.


Step 1. Create two folders named Windows Files and WAIK Files on your desktop or any other drive which has a minimum of 5 GB free space.

install windows 7 to an usb external hard drive

Step 2: Download the ZIP file from here and extract the contents to WAIK Files folder. Before starting the actual installation procedure, you need to have three files: Bcdboot.exe, Bootsect.exe and Imgex.exe. These files can only be obtained by installing Windows Automated Installation Kit for Windows 7 on your Windows PC. After installing WAIK, simply search for these files in the Windows installation drive to get them. Once you have these three files, copy them to WAIK Files folder that you have created in the above step.

Install Windows 7 to an USB external hard drive10

Step 3: Copy all the contents of Windows 7 installation DVD to the Windows Files folder.

Step 4: The next step is to run Installer.cmd file as Administrator (Right-click on installer.cmd and select run as administrator). In the first screen, you will be asked to press Enter to continue.

Install Windows 7 to an USB external hard drive15

Step 5: Press Enter key to browse to the install.wim file present in the Windows Files folder. The Install.wim file can be found under Sources folder (Windows Files/ Sources/ install.wim).

Install Windows 7 to USB external hard drive1

install windows 7 to usb hard drive

Step 6: Now, you need to select the Windows 7 edition that you want to install on external hard drive. You can select the edition by entering the index number shown in the screen. For example, type “5″ (without quote) and hit Enter key to select Ultimate edition.

Install Windows 7 to an USB external hard drive2

Step 7: The next step is to enter your External drive’s drive letter. Enter the drive letter (ex: L) and press Enter key.

Install Windows 7 to an USB external hard drive3

Step 8: Now, type in the drive letter of your ACTIVE partition and hit Enter key. Generally “C” is the active partition. You can find the active partition by opening Windows Disk Management tool (type diskmgmt.msc in Start menu search area and hit enter to launch it).

Install Windows 7 to an USB external hard drive4

install windows 7 to usb external disk

Step 9: Finally, the installer will ask you the drive letter that you have entered to install Windows 7 is a USB hard drive or not. As you are installing Windows 7 to an external hard drive simply type “Y” without quote and press Enter key.

Install Windows 7 to an USB external hard drive5

Finally click Enter key again to start extracting the Install.wim files. This might take a few minutes. Once done, you will be asked to reboot your PC to continue the normal Windows 7 installation procedure.

Install Windows 7 to an USB external hard drive7

Install Windows 7 to an USB external hard drive9

Step 10: Reboot your PC and follow the usual Windows 7 installation procedure to complete Windows 7 installation on external hard drive. Your PC will be restarted twice or thrice during installation.

Please note that the installation procedure might be slower as you are installing Windows 7 to an external hard drive.

Step 11: Once done with the installation, you are good to go. You can install all drivers and other software to start using the best Windows version on your PC.

Note: We have tested this method to install x86 flavor of Windows 7 to Seagate USB external hard drive. But should work fine with x64 as well. Users who would like to carry Windows 7 on a USB flash drive can follow our how to carry Windows 7 on USB flash drive guide.



  1. 4N0N says

    Yeah so when I load the install.wim, no images show up at all. I guess it doesn’t matter as this author isn’t doing jack **** to help anyone. Thanks for nothing.

  2. Saidou says

    I have a company HP Elitebook 8470p. Because I don’t have any privileges in Windows, I want to try this tutorial out.
    My question is as followed:

    (1) If I take out the internal drive and try above method, will it then create a separate MBR partition to boot?
    The problem is that booting from another drive/boot partition is locked by my company (tried it with Ubuntu).

    (2) I also don’t want to make changes to MBR partition of that internal drive so I won’t get in trouble with my employer :) When I re-add the internal drive will it then keep 2 separate MBR boot partitions or does it merge it?

    (3) My boot menu for the moment has folowing priorities: DVD-drive –> USB –> HDD
    So whenever the external drive is not connected it boots automatically from the internal drive, when USB-drive (Ubuntu) is inserted it boots from the USB drive. (no changes to internal MBR drive)

    Thanks for your help.

  3. Steve says

    I just noticed that it says “external hard drive” specifically. Does this method work on usb FLASH drives?

  4. Steve says

    I have the same problem as Archmaester. I get a “BOOTMGR is missing.” every time i try booting from usb. I tried repairing with a Windows 7 dvd (both automatic repair and manual from command lines) , nothing help.Anyone knows how to fix this?

  5. Richard Mangaliag says

    Please help i got this error message.

    [ 0%] Applying progress
    Error restoring image.

    A required privilege is not held by the client.

    The Wim file applied O.K.

    Processing the registry and usb boot watcher…

    Error occurred when loading the registry
    Press any key to exit..

  6. Archmaester says

    Did all the steps above without mistake …it took me 141 minutes to finish the procedure but after that i received an error “BOOTMGR is missing.” after restarting and booting in USB …

    How to Fix this? pls respond ASAP … my IDE Hard disk is dead 1 day ago and i need a temporary solution using this method …

  7. Jasmine says

    This tutorial does not work when you try to install Windows 7 on a hard drive using a computer with MacOSX, my computer couldn’t run installer.cmd

  8. Kyle says

    I am sorry to say that but your guide only worked for me until step 9. When the copy process was completed, I tried to reboot from the Install DVD, where I got the usual error (cannot install on USB …) and the try to reboot from the external HDD just gave me a flashing _ . So, what did I do wrong?

  9. Daniele says

    Thank you for this guide!
    I have two questions:
    1) Would it be possible to install Windows 7 on a SSD plugged into a USB docking station?
    2) After installing, is it possible to put the SSD inside the notebook and boot from there, or will there be disk-letter problems?

    Thank you in advance

  10. Martin Hidalgo says

    Thanks you very much, the system was installed perfect !!!… Easy to do with your instructions.

  11. Koray says

    Can I use windows7 installed external drive with different computers? This is a so important. If I can’t, it doesn’t make sense having windows7 on an external drive.

  12. admin says

    Thanks for your comment. It should work fine. I have tested it. Are you getting an error while attempting to boot?

  13. chris says

    Did all steps when I reboot didn’t go into windows 7 installation shows me 2 window 7 OS’s one works (internal HD) and the other does not (external HDD) states kernel debugger is missing or corrupted how do I fix this please help .I guess you cant since you just delete one of my comments

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