exe, .dll, .ico, or .bmp file in the DefaultIcon key??™s
(Default) value. (Hint: there are some nice icons in \Windows\System32\
shell32.dll.) Include a number to indicate which icon to use, or leave out the
number to use the first icon in the file. In some cases, Windows Explorer
will recognize the change right away, although due to the way Vista caches
icons, you may need to restart Windows for your change to fully take effect.
The easiest way to change an icon for a file type is with a
third-party tool like File Type Doctor, discussed in the next
section.
The only time when Windows won??™t pay attention to the icon specified in
the DefaultIcon key is when an IconHandler is defined. IconHandlers generate
dynamic icons on the fly (Figure 3-13), typically showing thumbnails of
the files??™ contents in lieu of static icons.
An IconHandler is a program??”typically a .dll file in the program folder of
the application with which the file is associated??”that understands the file
format. For instance, Adobe Acrobat (version 7.0 and later) makes use of
this feature to facilitate thumbnail previews for .pdf files in Windows
Explorer. For the .pdf filename extension, Acrobat??™s IconHandler could be
referenced in any of these Registry keys:
HKEY_CLASSES_ROOT\.pdf\ShellEx\IconHandler
HKEY_CLASSES_ROOT\.pdf\ShellEx\{BB2E617C-0920-11D1-9A0B-00C04FC2D6C1}
HKEY_CLASSES_ROOT\AcroExch.Document.7\ShellEx\IconHandler
HKEY_CLASSES_ROOT\AcroExch.
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