File types that are not registered with the system and files that have no extension, are assigned a generic icon from shell32.dll,0 resource by default in Windows.
The unknown or generic icon for unregistered file types and extensionless files can be customized as per your choice in Windows Vista, so that you don’t have to see the boring icon any more! This post tells you how to override the generic icon in Windows Vista.
Windows Vista stores the icon setting for unknown file types and extension-less files in this registry key:
