The installation disk should also have a copy of ViewNX. If not, you can download this from Nikon's site for free.
http://support.nikontech.com/app/answers/detail/a_id/61
This will allow you to save the image out as a JPEG or TIFF (16-bit or 8-bit per color). I believe it has rudimentary editing features like level control.
Unfortunately, Nikon wants you to buy CaptureNX for $150. It is a horrible piece of software. Better to buy Photoshop Elements for $80 and use the included Adobe Camera Raw to manipulate the raw formatted images.
If you want to edit raw, you need a good program. Adobe Camera Raw is very good. To take advantage of raw format, you also need a 16-bit image editor like Photoshop or The Gimp. ACR will only take you so far in editing. The Gimp is free, but not a pleasant user experience compared to Photoshop.
Unless you really need to shoot in raw mode, shoot in JPEG. You can still edit JPEG images, but you won't have the latitude of a 16-bit raw image. If all this sounds like mumbo jumbo, you really shouldn't be shooting raw until you understand the work flow of raw image processing.