If you have a photoeditor (photoshop or Nikon view) you can cut the picture size down enough that line speed won't matter. Some cameras will also cut the pixel count - check your manual.
Those huge 4-5 megabyte files are a pain to me, also, as I am on dial-up. But in almost every case, you can reduce them to under 100K without losing any significant detail, and that takes only a couple of seconds at dial-up speeds (and saves space on your drive as well).
Jim