Well, this thread was amusing... Where to start?
When an ISP says "no servers" they only care about servers that you make available over their connections. They can't even see inside your network! If you're running Windows server or even linux as a "server", as long as it's not accessible outside; the ISP won't know/care.
Right, Apple Inc! Domain controllers are a royal pain to set up properly. Are you sure you've successfully made your Server 03 machine into a Domain Controller with DHCP and DNS?
You might have to turn DHCP off on your router; so your local client machines get their IP addresses from your server (where you want them to!) Once this is done, the DNS should automatically be set to the server, and voila, you *should* be able to see the domain.If not, double check the DHCP and DNS services are running. Or just manually set them.
Once this is all up and running, the server has to be on at all times or the internet will brake on each machine. Do remember that! :)
Moving on; Windows Servers are just as secure if you keep them up to date, and the admin isn't a complete idiot. I run a Server 2008 box for my parents small business, with Active Directory and Windows Software Update Services.
Yes, I could probably do the domain controller using Samba on Debian (Incidently, my favourite linux distro!)... But thats just hassle I don't need. Plus, WSUS only runs on Windows and it saves a crap load of bandwidth! (The server downloads all Windows updates, and distributes them around the network.)
Oh, and you can run Apache on windows. If you want to.