OK not that conversant with the D80, but checking the manual it doesn't
appear to allow loading Profiles as you can with some (D300 in my case)
however I do note that even if FINE-JPEG there is a 1:4 compression
compared to the RAW image, so that will have a significant effect on any
noise.  Do you use Capture NX to process the images from RAW?  If so try
saving the image as the same size Pixel size as the JPEG from the camera
and adjust the compression ratio to achieve the same file size then compare
the two images.

Try using within the Capture NX the Base Adjustment, Detail Adjustment, and
adjust the Noise Reduction parameters to see if this will reduce the
problem, you can then save in TIF etc. for processing and gain the
reduction in noise without losing any further detail in JPG compression.