How to convert an NEF file to a JPEG file?

I have a nikon d3100 and i put my pictures on my computer and some of them are NEF files and i can't see them because it says "photogallery doesn't support this format or you need the latest verson of photogallery".so i downloaded it but it still doesn't work. And i read that you can convert them on photoshop but i don't even have photoshop and that would take forever cause i have so many pictures. How do you convert them all?

Download Nikon's ViewNX software to convert from raw (NEF) to jpg. You should also have a copy on CD/DVD that came with your camera.

http://support.nikonusa.com/...l/a_id/905