Did you promote the new dell server as a new domain controller? Once you do, make sure to move all the FSMO roles over to it. Once that has been confirmed, you should run the standard Ad health checks. Once it all checks out, then you should be able to demote the server by running dcpromo via the run command.
As per the SC440 and not detecting the hard drive you may need to use nlite to have the approrpiate scsi drivers installed during installation. Nlite will help create a new iso (windows 2003 source files needed).