Error during Exchange 2007 AD prep

Terribly need advice on this error..
After i completed the setup /PrepareLegacyExchangePermissions and setup /prepareschema, i continued with setup /PrepareAD and my exchange installation aborted with the error below.

My system running on single domain, co-existence with Exchange 2003

Summary: 5 item(s). 0 succeeded, 1 failed.
Elapsed time: 00:00:19

Organization Preparation
Failed

Error:
Active Directory operation failed on srvmaindc.localnet.mynet. The object ‘CN=All Contacts,CN=All Address Lists,CN=Address Lists Container,CN=Karangkraf-Ultimate,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=localnet,DC=mynet’ already exists.

The object exists.

Elapsed Time: 00:00:19

Copy Exchange Files
Cancelled

Hub Transport Role
Cancelled

Client Access Role
Cancelled

Mailbox Role
Cancelled

Thank you.