Install the new server and promote it using dcpromo.
Move any FSMO roles from the original child DC.
Move AD integrated DNS from original child DC if applicable.
Make sure there are at least two Global Catalogue servers in your network.
Use dcpromo to bring the original child DC down to a member server.
ok.....one other question then....I would like to use the
same name for the server....can i install it as a member
server with active directory move the roles and then
change the name after takeing the old server off-
line.....and then run active directory....
The process would be a little different if you want to keep the same name.
In this case, you should transfer all the roles, DNS, GC etc. to another
server and then dcpromo it down to a member server. Then it can be switched
off and delete the computer account from AD. Only then should you install
the new server and add it to the domain before dcpromo up to a DC.
You basically want to avoid any scenario that involves changing the name of
a server or, worse, a DC.