Hi Modcoms
As you have an additional DC already this is very simple and straight forward to achieve.
1: Demote Dc that you are wanting to replace to a member server. When you demote it all the FSMO roles will transfer automatically as part of the demotion to the remaining DC. As a previous poster said to seize the roles, this is not advisable and only used when a server that is holding the roles has died altogether. So in effect you would be using a sledge hammer to crack a nut!!
2:Rename the newly demoted server to a new name as you are wanting your replacement DC to have the original name and change the IP, assuming you want the replacement DC to have the same IP
3:Either build your new replacement DC using the name of the old DC and configure it with the IP of the old one, or rename it if its already built up with a temporary name.
4:Check DNS to make sure that any old NS records that were referencing the old dc are gone.
5:Run DCpromo on the new server to make it a dc
6:Allow replication to complete, this can take a while if there are ots of GPO's
7:Tranfer any FSMO's that you wish to transfer to it.
and voila!! There you have your new DC with original name
The risks: For a very short time you wil be running with one DC, if you time it right should only be a few minutes!
While you can aso use the netdom tool to rename a live DC it is not recomended to rename a Domain Controller, although it is possible.
Hope this helps.
