How to add Registry keys via DISM in Windows

If you’re building or customizing Windows images, DISM (Deployment Image Servicing and Management) is your go-to tool. It’s powerful, scriptable, and lets you inject drivers, updates, features—and yes, even registry tweaks—into offline Windows images.

This post walks you through how to add registry keys to a Windows image using DISM. It’s cleaner than trying to run post-install scripts and ensures your customizations are baked in from the start.

What You’ll Need

• A Windows image (WIM or ESD format)
• Admin privileges
• Basic knowledge of command line
• A reg file with your desired registry keys

Step 1: Mount the Windows Image

First, make a working directory and mount the image.

mkdir C:\Mount
dism /Mount-WIM /WimFile:"C:\Path\to\install.wim" /Index:1 /MountDir:C:\Mount

Tip: Replace the Index with the image index you actually want (run dism /Get-WimInfo if you’re not sure).

Step 2: Create a Registry File

Prepare a .reg file that contains the registry changes you want to make. Example:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\MyCompany\Settings]
"ConfigValue"="Enabled"

Save it as custom.reg.

Step 3: Load the Offline Registry Hive

You can’t just import a .reg file into the mounted image directly. You need to load the offline registry hive first.

reg load HKLM\OfflineSystem C:\Mount\Windows\System32\Config\SOFTWARE

Now the SOFTWARE hive from your mounted image is accessible under HKLM\OfflineSystem.

Step 4: Import Your Registry File

Modify your .reg file so it targets HKLM\OfflineSystem instead of HKLM\SOFTWARE.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\OfflineSystem\MyCompany\Settings]
"ConfigValue"="Enabled"

Then run:

reg import custom.reg

Step 5: Unload the Hive

When you’re done, don’t forget to unload the hive:

reg unload HKLM\OfflineSystem

Step 6: Commit and Unmount the Image

Finalize your changes:

dism /Unmount-WIM /MountDir:C:\Mount /Commit

This writes your changes back into the image.

Wrapping Up

That’s it. You’ve just added a registry key to a Windows image using DISM. This approach is great for automation, enterprise deployment, or custom builds that need pre-configured settings.

Have any registry tweaks you always include in your builds? Drop them in the comments.