Well for one thing you don't seem to have included the environment file in your zip so I can't tell if theres anything wrong with that.
Of the two graphic files in the zip (which I assume are part of the environment) one of them (stars.jpg) seems to be a bitmap file with the wrong extension (should be named stars.bmp). Thats probably the cause of your trouble. As far as I remember NL doesn't support .bmps so you will need to convert it to .jpg.
please post this kind of stuff over at coaster candy. your current one does not have all the files necessary so I will delete it right now. FOr that kind of stuff just use coastercandy.com for real tracks use this site.
WWS