Dont need Media Center anymore, just Windows Media Player V11.
I was struggling for about two weeks till I found out my onboard nVidia firewall was blocking all the required packets. I had turned on the firewall about a year ago, then unistalled the software cause it was crap. I assumed the software would deactivate the hardware firewall.
It didn't.
I had to re-install the software, disable the firewall, and uninstall the firewall software. But i doubt this is your problem.
I would suggest the following (assuming you want to share internet connection from laptop to xbox?).
Laptop:
Ip: 192.168.0.1
Subnet: 255.255.255.0
Xbox:
Ip: 192.168.0.2
Subnet: 255.255.255.0
Gateway: 192.168.0.1
DNS: 192.168.0.1
As a side note, I was playing Gears of War online, via my iBurst connection which is shared from my pc over the weekend, and I was completely blown away at how smooth, and LAG free it was. Also, my iBurst Account is actually in capped state (i.e. reduced bandwidth).
Once or twice i lost connection and dropped out of the games, but in general it was a whole lot more playable than what i expected.