Norton Protected Files are files that you have deleted, but Norton Protection allows you a second layer of protection, so you can recover a file deleted by mistake. If you don't want them you can empty the protected files. This feature can be turned off thhrough the Recycle Bin properties, as it takes up extra disk space.
No files are completely removed when you empty the Recycle\Norton bins, Windows merely marks the space as available for other files to be stored there. I suggest cCleaner, used by many here to wipe the space securely.