Windows Mobile 6.5 File Association Registry Settings

In Windows Mobile 6.5, mapping file extensions to default applications relies on the system registry under the HKEY_CLASSES_ROOT (HKCR) hive. This article outlines the specific registry keys, properties, and values that define these associations, detailing how the operating system links an extension to a Programmatic Identifier (ProgID) and executes the associated binary.

The Extension Key (HKCR\.<extension>)

The association process begins with the file extension subkey located directly beneath HKEY_CLASSES_ROOT:

  • Key: HKEY_CLASSES_ROOT\.<ext> (for example, HKCR\.txt or HKCR\.jpg)
  • (Default) Property: A string value (REG_SZ) that specifies the ProgID assigned to handle the extension (e.g., txtfile or pimgfile).
  • Content Type Property: An optional string value (REG_SZ) defining the MIME type of the file (e.g., text/plain), which integrates with the messaging and Internet Explorer Mobile subsystems.

The Programmatic Identifier (HKCR\<ProgID>)

The ProgID key defines application behaviors, context menu actions, and icons for the mapped file type:

  • Key: HKEY_CLASSES_ROOT\<ProgID> (matching the value defined in HKCR\.<ext>)
  • (Default) Property: A human-readable description of the file type (e.g., "Text Document").
  • DefaultIcon Subkey: Contains a (Default) property pointing to the binary and icon index used to render the file in File Explorer (e.g., \Windows\notes.exe,0).

Execution Verbs (HKCR\<ProgID>\Shell\Open\Command)

Windows Mobile 6.5 uses standard Windows CE shell verbs to launch applications when a user taps a file:

  • Key: HKEY_CLASSES_ROOT\<ProgID>\Shell\Open\Command
  • (Default) Property: A string value (REG_SZ) containing the absolute file path to the executable, followed by the argument placeholder: "\Path\To\Application.exe" "%1" The "%1" parameter passes the path of the tapped file directly to the executable.

Direct Extension Mapping (Compact Format)

In specific streamlined Windows Embedded CE implementations, file associations bypass the intermediate ProgID:

  • Key: HKEY_CLASSES_ROOT\.<ext>\Shell\Open\Command
  • (Default) Property: Contains the executable path and "%1" argument directly under the extension key rather than routing through an external ProgID.