SCCM Computers

That sounds like you activated the Active Directory System Discovery within SCCM. If you do not want the Clients to appear again, you must either deactivate or reconfigure the AD System Discovery or delete the Clients within AD if they do not exist anymore.
Also check if your Network Discovery in SCCM is enabled, this could also cause to create SCCM Client Objects

Thank you i will check it .... another question please how to create main collection like SITES and move the sub collections inside it.  

Please could you explain that more detailed?

I mean you know that there is many collections inside SCCM i want to make it more easy like creating a new collections example : ALL SITES and move my collections related to sites inside it like PARIS & ROMA...
i did that by following this guide : http://verbalprocessor.com/2009/03/20/how-to-move-collections-in-configmgr/
this is right ?

Yes create new instances by linking them and afterwards you can delete the original one

But the linked collection will have same configuration i mean any new resources will update automatically or no because the original collection deleted ?

Sorry i did not get you

i mean the original collection created based on AD site  now after i linked the collection and delete the original one it,s will have same configuration or not.