How to seize and remove FSMO roles

After decommissioning a domain controller, run NTDSUTIL at the DOS-prompt.

To remove the roles, you need to type the following:
1) metadata cleanup
2)connections
3) connect to server X (establishing a connection to the schema master (your primary domain controller usually))
4) select operation target
5)list domains
6)select domain X (x is a number)
7)list sites
8)select site X
9)list servers in site
10)select server X
11) remove selected
12) q

Repeat step 4 and 11 for a 2nd or 3rd demotion.