It depends what you are trying to do with the nwf, are you trying to import data into harnesses or schematics?
The nwf was really designed to send the wire data such as color, size, etc. from VeSys Design into Pro-E.
With VeSys 2008.2 it is possible to import wire lengths from Pro/E, the format required is XML. From within Pro/E, select "Wire List Export -> PTC Neutral", when the "Save As" dialog appears change the "Type" from "NWF" to "XML Wire List". This XML file can be read by VeSys Design,
I hope this helps.