Xbox 360 Media Extender Problems

[Jasebta]

I'm trying to set up my 360 as a media extender, following the instructions on xbox.com/pcsetup, but Media Centre says it cannot find an extender. I've tried google for help, but have found no solution.
I'm using Vista Home Premium if it's a help.

 

[Jasebta]

I'm leaving the 360 on the screen it tells you to leave it on when installing, and media centre still isn't picking it up.

 

[Jasebta]

At the moment it's on a wired connection through a Linksys router. It's recognized under Network, but it won't connect to it through the media centre.