Symptoms:
Want to migrate DC from Windows 2003 server to Windows 2008 R2 server. But DC1 who hold PDC no longer exist.
Solution:
Force moving FSMO to DC2 using ntsdutil
- ntdsutil
 - roles
 - connections
 - connect to server DC2
 - quit
 - seize PDC
 - seize schema master
 - seize RID master
 - seize infrastructure master
 - seize domain naming master
 - quit
 
Remove DC1 from AD using ntdsutil
- ntdsutil
 - metadata cleanup
 - connections
 - connect to server DC2
 - quit
 - select operation target
 - list domains
 - select domain 0
 - list sites
 - select site 0
 - list servers in site
 - select server DC1
 - quit
 - remove selected server
 - Confirm by click YES in message box (make sure removing DC1 server)
 
Remove any trails of DC1 record in:
- Active Directory Sites and Services
 - remove from server object
 - Active Directory Users and Computers
 - remove from server object
 - DNS
 - remove all DC1 ip records
 - remove from replicate