Windows CE Explorer, like Windows Explorer, allows you to customize a type name, as displayed in the details view of Windows Explorer, and an icon for any file extension (for example, .pwd). You must register file filters under HKEY_CLASSES_ROOT.
The following is the structure of HKEY_CLASSES_ROOT.
HKEY_CLASSES_ROOT\.<file extension>
\(Default) = <class name>
HKEY_CLASSES_ROOT\<class name>
\(Default) = <name to be displayed in the "Type" column of Explorer>
\DefaultIcon = <file name or index of the icon for this type>