WinPE: Store or split images to deploy Windows using a single USB drive

Article
10/12/2021

If your PC only has one USB port, you can still deploy Windows

The default Windows Preinstallation Environment (WinPE) drive format, FAT32, is used to boot UEFI-based PCs. FAT32 has limitations that you'll have to work around when working with most Windows images:

FAT32 has a maximum file size of 4GB in size. Most customized Windows images are over 4GB.
FAT32 has a maximum partition size of 32GB. Some Windows images are larger than 32GB.

(You can still use a 64GB or 128GB USB key, but you have to format it to use only uses 32GB of its space.)

Below are several ways to work around these limitations.

Option 1: Create a multiple partition USB drive

You can create multiple partitions on USB drives. To work with a USB drive with multiple partitions, both your technician PC and WinPE have to be Windows 10, Version 1703, or later.

Create a USB drive with WinPE and data partitions

Note

These steps require you to have the Windows Assessment and Deployment kit and WinPE add-on installed on your PC.

Open a Command prompt as administrator.
Run Diskpart:
```
diskpart
```

Use Diskpart to reformat the drive and create two new partitions for WinPE and for your images:

List disk
select disk X    (where X is your USB drive)
clean
create partition primary size=2048
active
format fs=FAT32 quick label="WinPE"
assign letter=P
create partition primary
format fs=NTFS quick label="Images"
assign letter=I  
Exit

Copy the WinPE files to the WinPE partition:

copype amd64 C:\WinPE_amd64
Makewinpemedia /ufd C:\WinPE_amd64 P:

Copy your Windows image file to the Images partition:
```
xcopy C:\Images\install.wim I:\install.wim
```

Option 2: Store the image on a separate USB drive

If your PC only has one USB port, you can deploy Windows using two separate USB keys:

Boot to WinPE.
After WinPE has fully booted, remove the WinPE USB drive.
Plug in a separate storage drive with your image and apply it to the device.

Option 3: Apply an image that's stored on a network location

Copy the image to a server on your network, for example, \\server\share\install.wim
Boot to WinPE.
Connect a network drive using a drive letter, for example, N.
```
net use N: \\server\share
```

Apply the image from the network.

Dism /apply-image /imagefile:N:\install.wim /index:1 /applydir:D:\

Option 4: Split the image

You can split a .wim file into smaller files that will be combined when you apply your image to a device.

Limitations:

Applying split image (.swm) files is only supported when all of the .swm files are in the same folder, as shown in these steps.
You can't modify a split .wim file.
When using a FAT-32 drive, you can format it to only use 32GB of space.
For images larger than 32GB, you need a second USB key because of the FAT32 partition size limitation.

From your technician PC, create your WinPE key. See WinPE: Create USB Bootable drive.
Open a Command prompt as adminstrator.
Split the Windows image into files smaller than 4GB each:
```
Dism /Split-Image /ImageFile:C:\images\install.wim /SWMFile:C:\images\split\install.swm /FileSize:4000
```
where:
- C:\images\install.wim is the name and the location of the image file that you want to split.
- C:\images\split\install.swm is the destination name and the location for the split .wim files.
- 4000 is the maximum size in MB for each of the split .wim files to be created.
In this example, the /split option creates an install.swm file, an install2.swm file, an install3.swm file, and so on, in the C:\Images directory.
Copy the files to the WinPE key.
On the destination PC, boot to WinPE, and then apply the image using DISM /Apply-Image with /ImageFile and /SWMFile options, as shown:
```
Dism /Apply-Image /ImageFile:C:\images\split\install.swm /SWMFile:C:\images\split\install*.swm /Index:1 /ApplyDir:D:\
```

WinPE: Identify drive letters with a script

Split a Windows image file (.wim) for FAT32 media or to span across multiple DVDs

DISM Image Management Command-Line Options