Okay, here's what I did. I followed the installation tutorial from introduction through to where it talks about installing with the older version of Blender. I downloaded the files it recommended and then installed them in the order they recommended. First I uninstalled all instances of Blender, Cobra, Nif Tools, Etc. Then I did a system clean up and rebooted the computer. Then I did this, as instructed in the tutorial: I got no errors while installing any of it. When I open Blender and go to "Import" from the File menu it offers these options: VRML 1.0, DXF, and STL and that's it. There's no option for Nif files. Does that help at all?