Well, first off, there really is no need to have a bunch of domain controllers on your network, especially given the size of your network. I would first remove the NT and 2000 domain controllers, making your Windows 2003 servers your primary and backup domain controllers.
The NT box, depending on whether or not you really need that old os for some legasy software or something, would make a great file server, or even better, a great planter (depending on your gardening skills).
That's your quickie solution, if your organization has some extra $$$, I'd at least upgrade the NT box to 2000 or 2003, or at best case, all of them... you'll find them working together alot better... Windows 2003, although Microsoft won't admit to it, has a number of issues with the old NT boxes, and they don't like to play nice with each other... as you try to share resourses, you'll start having more problems than you can possibly imagine...
Hope that helps... feel free to message me for more help...