Duplicate Records when you use Unknown Computer Support along with AD Delta Discovery

I’ve run into this scenario a couple of times after enabling Delta Discovery and have
got into the habit of doing a manual sweep for duplicate records, or extending
the Delta Discovery period, but that kind of defeats much of the reason for it.

http://blogs.technet.com/b/configmgrteam/archive/2011/08/17/known-issue-and-workaround-duplicate-records-when-you-use-unknown-computer-support-with-active-directory-delta-discovery.aspx

Basically, if you have Delta Discovery enabled and then image a new device
using unknown computer support SCCM creates a record for the new device, but
then if Delta Discovery runs before the Task Sequence installs the Client Agent
and after the OS has been joined to the domain, 2 records will be created
within SCCM.  The problems start though when SCCM can’t link/merge the two
together and won’t age either of the out of the database either.

Two choices are then left for you.

1. Manually
   sweep for duplicate records and delete the one that shows no client
   installed.
2. Setup a
   status filter rule that will run a script to automatically delete the
   record.

Thanks to
the TechNet article posted by Minfang Lv, this is now relatively simple to do,
with the scripts and instructions supplied.

As always, test before putting straight into production.