I'm testing the upgrade of our a domain environment from 2003 to 2012; Our environment consists of one DC (currently 2003 but will be upgraded to 2012 with this exercise).
I've transferred all FSMO roles, tested machine login, everything works. Windows clients are able to connect to the 2012 domain and environment functions properly even when 2003 was turned off.
My final step is to demote the 2003 dc to be able to upgrade the forest and domain functional levels. I run dcpromo on the 2003 dc and I get the error:
The network path was not found. If this computer is connected to the network via a remote access service (RAS) connection, ensure that file and printer sharing for Microsoft networks is enabled for that connection
The 2012 server has inherited services previously operating on the 2003 DC (Active directory domain services, DNS and DHCP