[H] XBOX 360 Question

[Winterlight]

I have a basic 4GB  XBOX 360s that I bought back in November to hook 
up to my HDTV and  use Media Center as a extender from my PC using a 
Silicon Dust Network tuner. It works great and I decided to buy 
another XBOX on Ebay for another TV and save the cost the renting 
another cable box. Today I bought a supposedly like new XBOX
 360s with a  320GB external hard drive and a couple of newish games 
= Halo 4 and Boarderlands2

In order to hook it up to my PC as another extender ( I know you can 
have 5 extenders) do I have to Activate it with Microsoft ... or 
change registration... or any thing like that... or can I just plug 
it in use my existing XBOX live log in and then  start using it.

-w-