How to recover CD key.

I have Office 2000 installed currently on my computer. Unfortuanately, I lost the CD case containing the CD key. I would like to recover the CD key in case I ever need to reinstall Office.

I have tried MagicJellyBean software and Belarc Advisor and they do not provide CD Key. I have went to Help and About and searched through the registry, but the only number is Product ID. I need the CD Key. Is there any way to recover this?

Thanks.