YEEAAHHH !! IT WORKS !!!
Thanks very much settingsun !!
I go in the MC setup menu on the xbox and at the end of the setup process, it give me the 8 numbers !!!
Then, I go on the PC, in the Media Center and put the code and... IT WORKS !!
If i do a network mapping, the interrupt line is still here but i think it represents the wifi connection.
Thousand of thanks !!!