Windows 7 - WMP 12 uPnP server still not working, no matter what.

Hello hello.

In a nutshell:

I can't get my laptop's Windows Media Player 12 uPnP server to show on any devices on my network.

I have at home my Windows 7 HTPC and an old XP desktop that is almost powered by coal. In addition there's a PS3, some mobile phones and an Internet Radio. On the HTPC I have WMP12 set to share though uPnP and everything works well. Phones can play music, the radio is happy as Larry and the PS3 (although a little temperamental) does what it's supposed to. No problems whatsoever.

I got a new Sony laptop recently. It's main purpose is for recording music, live band sets in particular, which I then play back to edit/review, so I'd like to listen via my radio when I'm in the kitchen or through the HTPC on the sofa. I have turned Media Sharing on using the obvious steps but cannot for love nor money seem to see the laptop through any of my other devices as a uPnP server. The PCs can see the laptop on the network and file-transfer is fine, but uPnP just says no.

My laptop can pick up the HTPC's uPnP, the phone's rubbish uPnP, my sister's Phillips hi-fi uPnP when I took my laptop round. Yet still nothing can see my laptop's WMP12.

Cue TVersity, Jamcast and Asset. They all work a treat. But not WMP. I have added exceptions to the firewall, I have disabled the windows firewall. I have trawled google. I've manually added ports to the firewall. I am totally stuck.

There is no anti-virus or 3rd party firewall on my laptop so I can't work out what the problem is. It's not my router because it happens elsewhere.

You may ask "why not just use a 3rd party server" but I need to use WMP.

Can anyone help?