If you have a load of XBLA games and arnt using your original console (who is?) then youve probably found you need to be signed in to play your games. However microsoft have seen the error of their ways and have created a nifty web page that lets you change the licenses to your latest console.
http://www.xbox.com/en-GB/support/drm/
It couldnt be simpler to do. Enjoy!