Al, thank you for your response and for taking the time to better understand the scenario I'm dealing with. The long range plan is to get onto a 2012 server platform, but we're not in a position yet to do a blanket replacement of all the equipment, and since the domain is still 2000 we're looking to do a staged upgrade to get to 2012.
1. Are your current DCs Windows Server 2000? - Yes
2. When you say can the existing 2003 servers be used as a DC do you mean leaving them installed as is and doing a DCPromo on it? - Correct. The lingering questions are if we make one of the 2003's a DC or both with one as a backup, will that hose the apps on them now (SQL Server/Sharepoint)?
3. What age are your physical servers? - About 10 years (Yes, they're old)
4. When you say to keep the demoted Server 2000 servers, do you mean not re-installing them? - Correct they would remain on the network running their current apps until we fully migrate them to eventual new servers
5. Do you have licencing restrictions, or is there money in the pot? - We would be dealing with some restrictions on licensing and are looking to take an economical approach to upgrading, if possible.