From Ardfry Imaging:
NEF codec is a plug-in for Windows Explorer, Windows 7 Media Center, Windows Photo Viewer, and Windows Live Photo Gallery. View NEF files throughout Windows, including NEF files from Nikon film scanners. NEF codec supports the latest Nikon camera models, including the D800, D3100, and Nikon 1 mirrorless interchangeable lens cameras. You can search and view metadata including broad support for lens data. See date taken, exposure information, and other details in Windows Explorer.