DSF or DUF files? There is the DSON or DAZ Scene Object Notation but I don't know of a DSO file. Dimension3D has a free script on his site. It won't work on P4. You need P9 or better and the free DSON importer script from DAZ. D3D also has the DSF toolbox over at DAZ that will convert DSF to obj files. It's stand alone but DSF, DUF and DSON are all DS4 files. These are many versions removed from P4 so I'm not sure how well the conversions would work.