Un-registering a console

Right so Over the years I have bought a couple of xboxes which I both registered online. I now want to get rid of the oldest one, I have done a hard drive reformat etc - but How do I find out the xbox consoles I have linked to my account and how would I go about removing the one I getting rid of?

If by you mean unregistering the serial code attached to your actual name, then I don't believe you can.

Thanks for the reply. yeah I did mean unregistering the serial number of the box. I am just thinking about security issues if I sell it on.

You could call up Microsoft before selling it and see if they can, but I'm not sure if they can or not. I've never actually tried it, I'm just guessing they don't for resale issues.