So far I've installed Blender 2.5.4, then installed Python 2.6.6, then PyFFI-2.1.5, then ran the installer for the NIF Scripts. The installer installed to stuff, but encountered an error trying to create two files. I figured out the problem was that it was trying to write files to the bpymodules folder, but the bypmodules folder was actually a file for some reason. A file with no extension.
So I changed that into a folder and ran the installer again. This time everything installed, but the import and export options still aren't showing up. Any ideas?