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Make a Bootable External Hard Drive and Install Windows 7/8

Step 1: Format the Drive
Just place the flash drive in the USB port of your computer. Open command prompt (cmd). You can do that by pressing WINKEY+R, right click on the listed file and click on “Run as administrator“.
Enter the following commands in the same order as I did here:

list disk
select disk z (where z is the number corresponding for your USB disk. You have to replace it with the corresponding letter from your own system).
create partition primary
format fs=fat32 quick

Diskpart Bootable USB

Please be careful using the select command (so you don’t select and format your hard disk instead)

Diskpart External Hard Disk

If everything goes well, this is how your cmd screen will look like

Step 2: Mount The Windows 8 ISO Image Into A Virtual Drive

If you don’t have a physical optical drive you should mount the image into a virtual drive. You can install and use PowerISO

Step 3: Make The External Hard Disk Bootable

I’m assuming that F is your drive letter with Windows 8 ISO image and G: is the location of your external hard disk (or flash drive) . Open the command prompt screen (as administrator) and type the commands:

cd boot
bootsect.exe /nt60 g:

External Hard Disk Bootable

Also, don’t forget to triple check the target location so you don’t accidentally delete the boot sector of your hard disk

Step 4: Copy The Installer Files

After the above step, don’t close the command prompt (at least not yet). At this moment your new external hard disk or flash drive is bootable but you need to execute one more command in order to transfer the files to your new drive. You have to type the following command line:

xcopy f:\*.* g: /e /f /h

Again replace the drive letters with the ones that apply to you. Alternatively you can copy all the files in the virtual drive to the flash drive or external hard drive by using Windows Explorer, but using XCOPY ensures that system and hidden files are also copied.

Step 5: Boot Off The External Hard Drive or USB Flash Drive

To use and boot from your newly created drive on your netbook or computer, first you have to set your computer you must set it to boot through the USB flash drive. In order to do this shut down your computer, go in the CMOS setup by pressing the “DEL” or “F2″ key when the computer power on, without unplug the newly created external hard drive or USB Flash Drive from the machine. Set the device as the primary boot option, save the changes BIOS and restart. On newer computers you can boot from the device without entering into BIOS by pressing either “ESC”, “F9″ or “F11″ (different key on different manufacturers).

External Hard Drive bootable

Now you can install Windows as usual. Please be aware that if you’ve changed the boot sequence in the BIOS, remember to change it back as it was after copying the files (usually after first automatic reboot).



  1. I was able to use these instructions to create a bootable HD for a 64bit Windows 10 install disk. Since machine was already 64 bit I used FS=NTFS instead. I used 7-Zip to extract the install files to a folder on the same external drive then ran the bootsect command to the already named external drive. It gave me an error about not being able to lock the partition but Bootsect command worked anyway. I then copied the contents of the install folder to the root of the external drive and rebooted. Works like a charm.

    Sorry to hear someone accidentally formatted there HD. The Hiren’s boot CD is an awesome tool for such problems and previously stated by another.

    I’d highly recommend the author ad another warning at the very top warning anyone trying this to have a complete HD backup in a different place just in case anything goes wrong. It is highly worth the time and trouble.
    Alternatively use another machine with nothing personal on it to create the external drive on so you don’t lose anything!

    Cheers and many thanks for a great writeup!

    • hi bob,
      can u do a video on this as guide and show us on youtube.
      really appreciate on this.

  2. Thanks for help, I’ll try these instructions and hope help me.

  3. hi when i was at the boot site to select the boot device
    it has an error
    ERROR; no boot disk has been detected or the disk has failed
    i follow as all the instruction and was all good, may i know what might be the problem ?

  4. It’s working. Thanks a lot.

    Nice article.

  5. Thanks man I really appreciate this tips it saved me from a dip sheet

  6. I don’t know much about doing advanced stuff like this, so maybe I shouldn’t try. Running the CMD as Administrator I do get the message “Acess denied” when I type “clean” for the selected USB-drive (also 1). Haven’t read all the comments below, but if someone knows what to do about it (asap) I’d be very glad to know.

    I was going to install a copy of W8.1 I got from a relative who bought it thinkng that an old XP could be easily upgraded. And was thinking about installing it on a USB-stick and updating to W10 before the 29th. I was going to install and use it on some other machine (a Mac) later and – although probably not possible to then upgrade it again to W10 – it still seems a bit unclar if this will be the case. So just in case…

    • Sorry guys!

      Seems I got the formatting part to work!
      First the USB-drive was reconised as a DVD-drive?! But running the cmd-process from the beginning, it worked.

  7. Think I’ll give up. Setting to boot from USB-drive and saving changes. But every time it still boots from ordinary drive. Going into BIOS to check, and it have by some reason changed back automatically! Tried a dozen times…

    • Well, that’s taking care of. Had to play around with all kinds of settings regarding the drives on the computer in BIOS. I have no idea what I really did, but now it boots from the external one. Unfortunatelly – when I now start to install Windows and choose were I want it, only the main HD on the computer is shown and all its partitions – not the USB-one.

      Have I formatted and/or installed the wrong ISO-files on the USB? I formatted with Fat32 as instructed, but I copied the 64-bit Windows version onto it? Maybe I should have copied the 32-bit version to it?

      • Nope… Tried with 32-bit files. But thats not it! Still no “Unit 1″ – the USB-drive it’s running/installing from – selectable.

  8. Very good, very clear, great job

  9. Is there a limit on the size of hard drive this will work? I have tried a 4gb and higher and when I got to format, it says The volume size is too big. Thanks in advance, Dione

    • just set fs=ntfs

  10. I had followed the steps described above and had created a bootable USB HDD. However, during install setup and after selecting language etc., when i choose to install win 10 on USB HDD, windows declines to go ahead stating that “Setup does not support configuration of or installation to disks connected through usb or IEEE 1394 port. A snip of error received is pasted below. At this point I even tried converting the USB disk MBR through CMD but nothing changed.

    Please help.

  11. Thank you so much . it worked d

  12. wondering how to put multiple os on it. win7, 8, 10. any guide

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