Really great post by Minfang Lv over at the System Center Configuration Manager Team Blog.
Read the full post here.
This post describes how and when you might see duplicate records when you use unknown computer support with Active Directory Delta-Discovery in Configuration Manager 2007 R3, what problems you might see, and some suggested workarounds.
Unknown computer support is an operating system deployment feature that was introduced in Configuration Manager 2007 R2. It allows you to find unmanaged computers so that you can install an operating system on them, and optionally, install the Configuration Manager client:
http://technet.microsoft.com/en-us/library/cc431374.aspx. Active Directory Delta Discovery is a new feature in Configuration Manager 2007 R3 that enhances the discovery capabilities of the product by discovering only new or changed resources in Active Directory Domain Services instead of performing a full discovery cycle: http://technet.microsoft.com/en-us/library/ff977086.aspx.
If you use these two features at the same time, you might see duplicate records for the unknown computer in Configuration Manager database. In this scenario, you will see two records in the Configuration Manager console that have the same name of the computer that installed an operating system by using unknown computer support: One record shows that it is a client and assigned; the other record shows that it is not a client and not assigned.