The Setup->File Associations->Default to WPS Associations menu item is used to toggle the priority of WPS associations over any conflicting defined FS/2 associations. When checked on, WPS associations have priority over FS/2 associations. When checked off, FS/2 associations have priority over defined WPS associations.
It is recommended that this option be disabled (default setup) and that the Setup->File Associations->Use Both FS+WPS Associations menu item be enabled (checked on). This setup will always use the FS/2 associations in priority over WPS associations but if there is no defined FS/2 association for a file, then the WPS associations will be used.