Not to be rude or anything, but that object is a mess. I'm assuming you created the window with a boolean operation, rather than slicing the mesh up and then bevelling the relevant section. Boolean operations should be avoided wherever possible when modelling for Poser. You've got triangles going in all directions and there are way too many polys for a simple wall. I'd start again quite frankly. It would probably be quicker that trying to fix what you have there.