i think this might help:

http://uk.gamespot.com/forums/show_msgs.php?board_id=909102863&topic_id=26517806

Hey guys,

I spent a lot of time trying to start the media sharing service between my PS3 and my computer.... it always gave me the dreaded 2104 DLNA error. I surfed many forums and the easiest solution was to use TVersity or Mezzmo. Many ppl could stream media using these 3rd party softwares. I was one of the few unfortunates who cldn't, so i installed linux and spent abt 5 hrs on it n finally saw succes in the form of YDL being able to access my windows shared folders, but even there, MPLAYER & VLC were giving me problems... the streaming was laggy and i faced many crashes... So, again, after spending a few more hrs, i was finally able to solve this problem. This solution will enable you to stream media without the use of any 3rd party software. Ok, now these are the steps to get it working:

• Get to your routers admin page and enable UPnP service
• Now, start services.msc from the run menu. (I'm using Vista Home premium and its showed up when i searched for it in the start menu)
• Look for the service SSDP Discovery, its not enabled by default. Double click on it and change its status to Automatic. You can also choose to give it a delayed start, so it dusnt affect ur boot up speed.
• Now look for the UPnP Device Hostservice and do the same
• Lastly, do the same with the Windows Media Player Network Sharing service

Now, I'm using Windows Vista, the other setting are Vista specific, but there shld be similar option for XP users:

• Go to your Network & Sharing Centre.
• It should say that u are connected to a private network, if not, click on customize and select the Private Network option.
• Next, go to Network discovery, change its status to ON.