Vista - xbox360 extender not found

I'm trying to set up my xbox 360 extender, and cannot get it to work.

Here's the setup, my Vista home premium PC is wireless conencted to a
netcomm nb8w modem/router. My xbox 360 is hard wired to the router. The xbox
works fine on the internet (ie live etc) it has a network address, and it
gets the 8 digit setup code.

My PC however does not detect the xbox in the network at all, and when
trying to add an extender through windows media centre, it cannot find it.

The first thing i tried to check was obviously that upnp was allowed in the
windows firewall, but i cannot find the option for it anywhere in the
exceptions list? i remember there used to be a check box for it in XP...

I've read through all the posts on here, and i cannot find any solution to
my problem.

Please help!

I just got my 360 connected. It didn't go as smooth as I would like.

After I punched in my 8 digit code on my PC, Vista couldn't find it. Finally I realized after I shut down MC, vista was waiting for permission to install device drivers. It couldn't find them on the WEB. I had to point Vista to C:\Windows to find the drivers. Only after that did the setup go smooth.