After adding a new 2012 DC to our existing 2003 DC we ran into some issues. The fsmo roles have been transferred but when any computer browses the network most of the computers don't show up. Why is this happening? I can map to each computer if needed but the names are not coming up in the network page
Check out Advanced Network Sharing settings (particularly turn on Network Discovery as suggested above). Make sure the network card is attached to Domain and not Public or Private.
Is the problem computer seeing the original DC? Is there a conflict between Domain Controllers? Perhaps the roles did not all transfer correctly. There is otherwise no issue for me to browse Server 2012 and its computers.
The Microsoft Server topic includes all of the legacy versions of the operating system, including the Windows NT 3.1, NT 3.5, NT 4.0 and Windows 2000 and Windows Home Server versions.