Can not connect 360 as an extender!!!!!

This is driving me round the bend so I hope someone can help me

My 360 is wired to my Dlink router just as the PC is, the routers IP is 10.1.1.1 the PC (Seven Ultimate) is .2 and the 360 is .3, these are static not DHCP from the router. I have no problem with internet connection on the 360 or with viewing media from the PC (my music, my video, etc). However making it a media center extender is just a no go. Within a few seconds of punching in the code given for connecting I'm graced with "an error was encountered while configuring your computer for use with this extender."

Now you'd think a MS product attempting to talk to another MS product could give you a bit more info!! I've googled this and gone through deleting the media center certificate, removing the mcx(?) user account and removing media cetner from the 360 memory but it just never works. I've always had windows firewall disabled (POC) and have attempted with the routers firewall settings disabled, all different levels of UAC. Follwoing are details from event viewer:


INFORMATION
Media Center Extender Setup started with the following settings:
Affiliation code: 321
Username: Michael


INFORMATION
Media Center Extender Setup has determined that the Windows Firewall is off.


INFORMATION
Media Center Extender found:
ID: uuid:10000000-0000-0000-0200-0017FA66137E
IP Address: 10.1.1.3
Interface GUID: {2fd0fdaa-aaa4-4011-9979-9b416f90c806}
NHED type: X02


INFORMATION
Media Center Extender Xbox 360 Media Center Extender 'uuid:10000000-0000-0000-0200-0017FA66137E' discovered at address 10.1.1.3.


ERROR
Media Center Extender Setup cannot create an account for the Extender with ID: uuid:10000000-0000-0000-0200-0017FA66137E.
Error: The system cannot find the file specified.

Can you refer me to links of steps you've already tried? I seem to have a similar problem but have not tried all the steps you have. I would like to see if any of them fix my issue. I had recently had the Xbox connected to my laptop, but reinstalled Windows 7 to Ultimate, from Home basic. Now my xbox does not see the PC at all.

Very frustrating, been there. This worked for me rather simple. Don't touch anything else leave as before (firewall etc.) go to control panel Network and Sharing Center. Click on manage connections.Right click on your broadband connection and click on properties. make sure the box that says allow others to use internet connection IS UNCHECKED. Do the same for your LAN connection. Save and then try WMC from xbox. Should now connect. Good luck.