Proper way to demote old domain controller (window2003DC) from windows 2008 r2 network

Hi

We have windows 2008 network ,including 1 2008R2 DC,12003 SP2 DC,1 exch2010 .

But  we shutdown 2003 SP2 server for 2 month for some purpose.

Now we  need to plan to demote windows 2003 SP2 .

Currently we got  some error and warning from directory service log.

One error is event id1864  and also got event id 2092 warning.

Let me know the proper way to demote old dc (windows 2003)

Thanks in advance