To use a throbber download a zip file from below, extract the two files,and rename them to 30m.bmp and 48m.bmp,then put them into the directory that contains the netscape.exe file(rename the ones currently there to something else..but remember what you rename them!)
Restart netscape and there is your throbber
To restore the N simply delete the two files 30m.bmp and 48m.bmp. and put the first ones back to their original names

How To Put These Throbbers Into Netscape 4(Communicator)
I've done this in my Netscape 4,and it works the same as in 3,so if you have problems,email me with the problem and I'll try to help you out:)

Notes: the Prefs.js file is located in the: c:\program files\netscape\users\YOURNAMEHERE\ directory. When you open the prefs.js file use Notepad or Wordpad.

1) Extract the two files into the directory containing the netscape.exe file
2) Open your prefs.js file
3) Paste the following at the bottom of the file:

config("toolbar.logo.win_small_file", "30m.bmp");
config("toolbar.logo.win_large_file", "48m.bmp");
config("toolbar.logo.frames", 11);
config("toolbar.logo.url", "http://geocities.datacellar.net/Area51/Vault/3780/throbbers.html");

Where 11 would be the number of frames in the bmp file (open it with paintbrush to count the frames)

4) Save the file
5) Set the file to be read only (Which means you'll want to have your preferences/options set before you do this)
6) Enjoy the throbber.

	Preview		Description		Download
			The Cute Dancing Baby		baby.zip
			A Purple Rotating Star		prpstar.zip
			A Swimming Fish		fish.zip
			Bear With Floating Balloons		bear.zip
			Spinning Packers Helmet		gbp.zip
			3-D Spinning Heart		heart.zip
			A Blooming Rose		rose.zip
			A Spinning Moon		moon.zip
			A Skier Zoomin Downhill		ski.zip
			A Norn Casting a Spell		wiz.zip

Ok well thats all I've made so far,maybe I'll get around to more:)
If you have any requests...email me and I'll see what I can do for you.