1. Start -> Control Panel -> Add/Remove Programs -> Add/Remove Windows Components
3. Go to Networking and click details
2. Tick the “Peer-to-Peer service” option and the “UPnP User Interface” option.
4. Click OK to get out of those dialogs, Windows will install some stuff for a minute or two, then try sending a file again.
5. Sit, Enjoy and wait for futur msn bug to pop in your face :P