This is the basic program to work with .NEF extension

FastStone Image ViewerFastStone NEF File

FastStone Image Viewer provides you with a practical and alternative way to enjoy your photo collections - you can view each photo in full-screen mode with high quality and in full detail. However, the program does much more than its name suggests, as it can also edit and convert your images in batches, compare them, create stunning slideshows, print your images with full control, and more... (more) The program works with the following extensions: wmf, bmp, gif, jpg, png, psd, jpeg, tga, cr2, crw, dng, mrw, nef, orf, pcx, jpe, pef, raf, srf, arw, tif and tiff

.NEF extension is also supported by the following programs:

	Capture NXimage/nef
	Capture NX 2 is a full-featured non-destructive photo editing program.

	PaintShop Photo ProPaint Shop Pro Studio Image
	Photo-Editing software for amateur photographers and profesionals.

	FastStone MaxViewMySQL Tools for
	Enjoy your photos in full detail and edit them in various practical ways.

	Zoner Photo Studio XRAW bitmap image
	Create, manage, edit and enhance your photos through an all inclusive software.

	FiregraphicRAW Image
	Firegraphic is a powerful tool for organizing and editing photos.

	ArcSoft PhotoStudio DarkroomMySQL Tools for
	PhotoStudio Darkroom lets you edit and apply enhancements to your digital photos.

	MAGIX Photo Managernef Raw-Image
	Photo Manager lets you present your photos and videos impressively.

	cam2pccam2pc Image File
	You can manipulate images from your computer or camera.

	Corel Paint Shop ProPaint Shop Pro 9 Image
	Corel Paint Shop Pro is a complete graphics package.

	Smart Pix ManagerSmart Pix Image
	Smart Pix Manager - management and viewing of all types of media files.

	ACDSeeACDSee 8.0 NEF Image
	Organize, edit, and share your photos with ease.

	MaxIm DLMaxIm DL Image
	Collects, manages and analyzes astronomical and science data.

	cam2pc Freeware Editioncam2pc Image File
	cam2pc Freeware Edition 4.6 is a program to browse, view and download photos.

	Nero StartSmartNero Encrypted File
	Nero Startsmart is a Nero's one-click project launcher.