First off I think your camera kit came with some software called Picture Project, and /or ViewNX that can convert the RAW NEF files to jpg. I may be wrong on this but check it out.
Second off is something free but I have never used it so I can't give a nod either way. Check out Raw Shooter Essentials
You can alsodownload a free trial of Nikon's Capture NX
(scroll down half way) software and use it for 30 days. It costs about $130 if you want to own it.
You could also download the trial of Adobe Lightroom
30 days also, costs $300.00