== random links == * MSDN Creating Icon Handlers * The Code Project: Create Thumbnail Extractor objects for your MFC document types * MSDN: Creating Shell Extension handlers for Windows
associating the extension
Create a key HKEY_CLASSES_ROOT/.ext with value "Extension Class Name"
Create a key "HKEY_CLASSES_ROOT/Extension Class Name/ShellEx/{BB2E617C-0920-11d1-9A0B-00C04FC2D6C1}" with the GUID of the class with IPersistFile and IExtractImage interfaces.