Im having a very similar if not identical problem, I installed Media Center on my PC, then i download Windows Media Connect, installed it, but during installation, it does not ask me for the security code. The code is in the format xxxx-xxxx. During the install it says it is authorising my xbox 360, and the end it says it has been authorised.
I have been in the newbie forum discussing this, and someone posted screenshots of what is supposed to happen during Windows Media connect install, and it very clearly asks for the code.
The only difference between XP and Media Center as far as i can tell is that installation options are limited and in Accessories from the start menu, there is media center functionality.
How would we tell if we had a * ahem * dodgy version of Media Center?
Should we try one of the other versions of windows media connect that are available from the Xbox website?
and what is update rollup 2, and how do i determine if it is installed?