What you need is a uPnP Server application/service which will host your media which can then be accessed via a uPnP client
I'm running Windows Home Server 2011 which is pretty much under the skin Server 2008. I'm using PS3 Media Server, in the settings have you specified the IP address you have assigned to the server(statically I'd hope) I found that it simply didn't work if I hadn't. Another easy mistake is to not add the folders containing the media you want to share. PM me if you want, I have a setup that is working across multiple devices!