A developer was working on a context-menu shell extension. He registered the extension under:
The developer noted that his context-menu extension was called for all files. But he also wanted his extension to be called for all directories.
If you want your context-menu shell extension to be invoked on all files and all file folders, the correct key to use for registration is HKCR\AllFileSystemObjects, not HKCR\*.
For more information, MSDN has a list of Predefined Shell Objects.