To decomission an Active Directory Domain Controller (Windows Server 2003/2008) is a fairly straight forward task as long as you make sure nothing is relying on that server.
What to check before decomissioning your DC
The most important thing to check before you are decomissioning your DC are the following components that are either running or registrered against the system:
- Global Catalog
- FSMO Roles
- Bridgehead server
- General server health
- Enterprise admin credentials