I have the internet connection set up and tested, all is ok. I cannot see it on my computer network nor any music or pics on my menu of the HR20. I tried all of the helpful hints in this forum with no luck. In WMP11 file sharing no devices are listed.
Here's something that worked for me when I had the same problem.
Go to "Start" click on "Control Panel" then click on "Administrative Tools" then click on "Services" go down to "SSDP Dicovery Services" and double click. Make sure you are looking under the "General" tab. Now go down to "Startup type" and select "Automatic" from the drop down box, then click "OK".
Now find "Universal Plug and Play Device Host", further down on the "Services" list, and double click on it. Make sure you are in the "General" tab again, and go down to "Startup type" and select "Automatic" from the drop down box, then click "OK".
Now you can close the "Services" window and the "Control Panel" window. Now open up "WMP11", go to the top and select the "Tools" tab then click on "Options" then click on the "Library" tab then click on "Configure Sharing....", then enable sharing. Hopefully you will get the "Unknown Device" which should be your HR20 and all should work.
This worked for me, but to clarify mine was showing Internet and Network connected before I did this. I figured this out from looking at the error messages in the "Event Viewer" which is also accessed from the "Control Panel" then "Administrative Tools" then "Event Viewer" then the "System" which brought up messages including error messages. Just double click on an error message to see what's going on when you are trying "Configure Sharing".
If you haven't tried to configure sharing in WMP11 do that before you try what I did above.
Hope this helps,
FYI, I am running a Gateway with Windows XP Media Center Edition with WMP11. Am hardwired from HR20 to a Netgear WGR614 v5 Wireless router. My computer is hardwired into the router as well.