Replace 2000 domain controller

I have a pair of Windows 2000 domain controllers. The machine that currently hosts GC is getting tired and is pretty old as far as hardware. I want to replace it with a newer machine I have lying around. Ideally I want to keep the same name and IP address though that is not neccessarily critical. Furthermore I have a license for 2003 server that is not in use so the new machine will run 2003 server. Any advice on the basic step by step?

As you have 2 DC's this makes it a much easier task, I would do the following:

If you wish to use the same name and IP, you can do it this way:

1. Transfer any FSMO and GC roles held by the server to be decommisioned to the other.
2. Run DCPROMO to demote the server from a DC to a member server
3. Remove the server from the domain altogether and turn off
4. Bring up the new server, set its name and IP
5. Join the new server to the domain
6. Run adprep to prepare the domain for server 2003 DC's - See here
7. Promote the new server to a domain controller in the existing domain
8. Transfer and FSMO roles you wish to host on this DC, set as GC if required

If you are not concerned with using the same name and IP, this is probably the better order:

1. Bring up the new server, set its name and IP
2. Join the new server to the domain
3. Run adprep to prepare the domain for server 2003 DC's - See here
4. Promote the new server to a domain controller in the existing domain
5. Transfer any FSMO and GC roles held by the server to be decommisioned to one of the others.
6. Run DCPROMO to demote the server from a DC to a member server
7. Remove the server from the domain altogether and turn off

Obviously before you get rid of the old server you want to have a full backup of everything and ensure any required data has been moved off to the other servers.