Xbox 360 Setup Key Lost

http://www.winforumz.com/windows/Xbox-360-digit-set-key-ftopict651468.html (Xbox 360 8-digit set up key)
I have lost the 8-digit setup key. How do I get the Xbox 360 to redisplay the set-up key?
« Remove the Extender affiliation from Media Center and delete the Extender info from the XBox 360. Then re-add it as a Media Center Extender. A new 8 digit code will be generated. -- Doug Knox, .. »
« My OS Windows7 ultimat64.Lost my windows media center Xbox360 8-digit setup key »

http://www.winforumz.com/windows/xpmce2005-connect-xbox360-ftopict658028.html (xpmce2005 will not connect to xbox360)
system was working in the past, now i am trying toget my 360 connected to my mce. i retrieve the setup key for 360, run the extender setup program on mce, enter setup key, and mce says it can not connect. i have turned off all firewalls (router, and windows). has anybody had this problem?
« It looks like mce is finding the xbox om the network during setup, it is not verifing the setup key from the xbox... Any help???? thanks »