This class allows applications to store and retrieve user and system preference and configuration data. This data is stored persistently in an implementation-dependent backing store.
Question : On Windows, where are the JAVA user preferences stored ?
Answer : In the registry. Typically in HKEY_CURRENT_USER\Software\JavaSoft\Prefs\[your path] If you want to change your storage (i.e : backing store) you will need a new PreferencesFactory, as detailed in this post.