active directory – join as child later??

I have a parent domain in active directory. I’m having issue currently trying to join a new win2k server as a child, but need to get it up and running TODAY. If I make the new server a new domain, with a new domain tree, and a new forest of domain trees…can I later join this domain as a child to a parent? Or would have have to uninstall active directory (losing all my accounts!) and reinstall it?