need to remove the dc server

I have 3 windows 2000 servers 1 is just the proxy/email server and the other two are for the domain. On the primary domain server I have dns installed. On my primary domain server I belive the Active Directory is Corrupt. All of the applications that we use are not working correctly. We had a hard drive go bad. I am now getting ready to rebuild this server. I know I need to move the DNS to another place. What kind of other trouble will I have to look for or should I say what problems can I expect when I take this computer off line to rebuild.

Thanks for all of your help