Many Computer Names for one IP in AD

Hi there,
I’m managing a park of 1200 computers under Windows XP in a Windows 2000 Server with active directory. I use Norton Ghost and Sysprep to deploy new images on computers and I have automated the process of re-naming the computer and create that new name in the active directory.
The probleme is when I have to re-image computers for adding a program or service pack, the old name of the computer is still in the AD and a new name comes in the AD. In my DNS database, I can see that for oneIP address I may have sometimes 20 computer names.
My question is: how can I get ride of old computer names safely and automaticly?

Thank you for your answers…

Cyril