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Understanding Windows Image Files and Catalog Files

Applies To: Windows 7


This content applies to Windows 7. For Windows 8 content, see Windows Deployment with the Windows ADK.

Windows┬« System Image Manager (Windows SIM) uses Windows image (.wim) files and catalog (.clg) files to display the available components and packages that can be added to an unattended answer file (Unattend.xml). Windows images and catalog files contain configurable settings that you can modify once the component or package is added to an answer file.

Windows Image (.wim) Files

A .wim file contains one or more compressed Windows images. Each Windows image in a .wim file contains a list of all of the components, settings, and packages available with that Windows image.

Limitations of .wim Files

The following list describes some of the limitations of using .wim files.

  • Windows image files can be opened only by an account with administrator privileges.

  • Windows image files can be opened only by one user at a time.

  • Because Windows image files can contain one or more Windows images, they tend to be large. Some Windows image files can be several gigabytes (GB) in size.

  • The settings in a Windows image can change over time. Windows SIM enables you to create an answer file in which the settings are modified, added, or removed. Windows image files also change when packages are added, configured, or removed. By running Setup and then applying the answer file, the new settings and configurations are applied. If you recapture the installed Windows image by using the ImageX tool, the new settings and configurations are now the defaults. When a Windows image changes, you must create a new catalog file.

Because of these limitations, Windows SIM uses catalog files when creating an answer file.

Catalog Files

A catalog file is a binary file that lists the state of all the settings and packages in a Windows image. When a catalog file is created, it queries the Windows image for a list of all the settings in that image. Because the contents of a Windows image can change over time, it is important that you re-create the catalog file whenever you update a Windows image.

Because Windows images can be opened only by administrators, you must have administrator privileges on the system to create a catalog file.

The Windows retail DVD includes pre-generated catalog files for each Windows image inside the Install.wim file. These catalog files are in the \Sources directory of the retail DVD and can be used to create an answer file for a Windows image in the default Install.wim file. However, if you intend to create a catalog file for a custom Windows image, you should use Image Manager to re-create the catalog file for that custom Windows image.

Contents of a Catalog File

The catalog file contains the following information:

  • A list of component settings and current values.

  • Windows features and package states.

Benefits of Catalog Files

Catalog (.clg) files have several advantages over .wim files.

  • The size of a .clg file can be less than 1 megabyte (MB), while .wim files can be several GBs in size. Also, .clg files are easier to copy to removable media or a network share.

  • While .clg files enable multiple users to create answer files for a single .clg file at the same time, a .wim file enables only one person to open and to access the .wim file at any given time.

  • Non-administrators can create answer files for a .clg file. However, .wim files can be opened only by administrators.

Troubleshooting Catalog Creation

In some scenarios, you might not be able to create a catalog for a Windows image. The following list describes some of the common causes and workarounds.

  • Catalog creation fails when the .wim file is in a read-only location, such as on a DVD. The workaround for this issue is to copy the .wim file to a location that has read and write permission for the current user.

  • Attempting to create a catalog file for a Windows Vista┬« RTM image fails. This is not a supported scenario with this version of Windows SIM.

  • Windows SIM fails to create a catalog for a 32-bit Windows image from a 64-bit version of Windows SIM. To workaround this issue, use the 32-bit version of Windows SIM to create catalogs for your Windows images.


Different binary versions of Windows SIM cannot create catalog files for some Windows images of different architecture types. We recommend using the 32-bit version of Windows SIM to create catalog files because this version can create catalogs for all Windows image architecture types. The following list describes the Windows SIM architecture types and catalogs that can be created for each Windows image architecture type.

  • x86 Image Manager. Can create catalogs for x86, x64, and Itanium-based Windows images.

  • x64 Image Manager. Can create catalogs only for x64 Windows images.

  • Itanium-based Image Manager. Can create catalogs only for Itanium-based Windows images.

See Also


Windows SIM Terminology
Windows SIM Architecture
Windows System Image Manager User Interface
Understanding Distribution Shares and Configuration Sets
Understanding Answer Files
Understanding Settings and Properties