LR is color managed whereas Windows viewer is not. Is you monitor calibrated?
First, try to reset to the default sRGB color profile for the monitor: http://www.lightroomforums.net/showthread.php?14070-How-to-assign-an-sRGB-ICC-Profile-to-y our-monitor-%28Windows%29
Are the photos JPG or NEF?
You can not change the color profile of LR.
My monitor is calibrated with a Spyder4. My photos are NEF. I reset the default sRGB until I read the rest of the article that said this only worked until you got something to calibrate your monitor, like a spider, so then I set the default back to the last one I calibrated with my Spider4. My color looks to be perfect on the Windows Photo Viewer, which is a different application then the other photo viewer I was looking at before, but it can't do what LR does, or is suppose to. I have been on the phone with Adobe for 3 hours in the past 2 days, and they still don't know what wrong. I would appreciate any additional help.
Did you try to recalibrate with your Spyder?
If not, please try this and see if this helps.
Absolutely. Any color troubleshooting always begins with the monitor profile. That's usually where the problem is.
Any further differences are usually explained by applications that aren't color managed to begin with, and just ignore the profile. For instance, Windows Photo Viewer is color managed, but the new "Photos" app in Windows 10 isn't. So they won't show the same.
However, the flip side of this is that a defective profile will only affect these color managed apps, the others display just as they always did. Furthermore, a defective profile may affect different color managed applications differently.
All that said, Lightroom and Nikon Capture NX will always have slightly different interpretations of how the file should look at default settigs. That's normal and fully expected and is unrelated to this.
Since you calibrate I doubt your monitor profile is the problem. There are two issues you need to be aware off in addition. First is that you might be applying auto tone adjustments upon import, a camera default, or a preset in the import panel. Make sure you have those all set at default. Go to Preferences->presets and uncheck the auto tone options and reset all camera defaults and check your import pane. On any already imported images, you can just hit the reset button and it should go back to a fairly bland default Lightroom rendering. Most people consider that to be a way to bland rendering so you might get the opposite problem so the second setting you should be aware of is the camera profile setting. You find this in the calibration settings in Develop. If you shoot a major camera brand, you will find a series of profiles there that are designed to mimic the in-camera jpeg rendering that you see when you look at the display on camera (every raw file has a jpeg embedded in it) or when you look at a raw file in most software not designed to deal with raw files where often you just get shown the jpeg preview. When you set this to the same setting as you are using in camera, the Lightroom rendering should be pretty close to what you see in camera or in the camera-manufacturers software at least if you do not use any other in-camerra settings.