JSI Tip 9152. Common file type Value Names and sub-keys.

File types, like .txt or .jpg are defined in the registry at HKEY_CLASSES_ROOT.EXT, where .EXT represents the file extension, like HKEY_CLASSES_ROOT.txt or HKEY_CLASSES_ROOT.jpg.

NOTE: It is important to include the leading period.

The common Value Names and sub-keys of a file type, HKEY_CLASSES_ROOT.EXT, are:

    Default Value   This string data type sets the PROGID, like txtfile or jpegfile. see HKEY_CLASSES_ROOTtxtfile.    PerceivedType   This string data type, not used prior to Windows XP, defines the preceived type, if any, and may be:                           Image                           Text                           Audio                           Video                           Compressed                           System     Content Type    This sting data type is the MIME content type, like audio/aiff or text/plain.                     See HKEY_CLASSES_ROOTMIMEDatabaseContent Type.    OpenWithProgids This subkey contains a list of alternate PROGIDs for this file type. They populate the Open With dialog.                    The Value Names, like AIFFFile and jpegfile are REG_NONE data types.    OpenWithList    This subkey contains application subkeys that populate the Open With dialog, like wmplayer.exe.                    The application must exist at HKEY_CLASSES_ROOTAppID, like:                                  HKEY_CLASSES_ROOTAppIDwmplayer.exe                                       AppID       REG_SZ  {B8C54A54-355E-11D3-83EB-00A0C92A2F2D}