the forum is here for other to see and learn from the troubleshooting done publicly.
as for the xAMP service - Apache, PHP and MySQL are very easy to install under windows. just look at the XAMPP packega from apachefriends, or get them separately and install. the web is full of tutorials. no need for IIS there.
about the domain issue:
setting up a domain in w2k3 is a breeze - just type dcpromo in the command line and the wizard will do everything.
external domain users might be slightly harder to implement, because that will mean you either stick the server out into the internet with the RPC port open (not wise at all) or set up VPN services, for the clients do dial in before the log onto the domain.
setting up win2k3 as a VPN+Radius server is easily googlable as well.
the question is - what do you need external users to join the domain for?