Sunday, January 6, 2019

Installing Windows from a USB Flash Drive

By Steve Endow

UPDATE:  I have discovered an easier solution:  Rufus

"Rufus is a utility that helps format and create bootable USB flash drives, such as USB keys/pendrives, memory sticks, etc."

The method below does still work, but in most cases, I've found that Rufus is simpler and works just as well.  It also has some nice enhancements for Windows, allowing you to default some setup options, like skipping the privacy questions and setting up default local accounts.

It also works well for Linux boot drives.


I'm currently building a new dedicated Windows server for running Dynamics 365 Business Central Docker images.

Since I only build a new machine every 2-3 years, I always have to lookup how to setup a bootable USB flash drive with the Windows installation files.

I am confident that I will forget this information in 2 weeks, so I'm posting this for posterity.

Here are the two articles that I used.

I initially tried to use Windows Disk Manager, but it didn't allow me to set the USB partition to "Active".  So I had to use the steps from this first article to set the active partition.

Prepare the USB drive using DiskPart:

Insert USB flash drive
Administrator Command Prompt
list disk
select disk <#>         (make sure to select the correct disk for your USB drive!!!!)
create part pri
select part 1
format fs=fat32 quick

And because Windows ISO images now have files larger than 4GB, you can't copy them to FAT32 file systems.  So I had to use the commands from this article to copy the Windows installation files to the USB drive.

After mounting the Windows ISO file so that it shows up as a new drive letter, run the two commands listed at the bottom of the article.  Make sure to set the drive letters to match your source and destination drive letters.

Copy the files to the USB drive using Robocopy and DISM: (commands at bottom)

In this example, the D: drive is the mounted Windows 10 ISO.  The E: drive is the USB drive.

Copy files smaller than 3.8GB (everything but the Windows image file) from the ISO to the USB drive:

    robocopy D: E: /s /max:3800000000

Split the Windows image file (from the mounted ISO on D:) and copy them to the USB drive on E:

    Dism /Split-Image /ImageFile:D:\sources\install.wim /SWMFile:E:\sources\install.swm /FileSize:3800

Steve Endow is a Microsoft MVP in Los Angeles.  He is the owner of Precipio Services, which provides Dynamics GP integrations, customizations, and automation solutions.

You can also find him on Twitter and YouTube

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