From microsoft:
http://www.microsoft.com/windows/windowsmedia/player/faq/sharing.mspx
1. Click Start, click Run, type regedit, and then click OK.
2. In the registry tree (on the left), expand HKEY_LOCAL_MACHINE, SOFTWARE, Microsoft, MediaPlayer, and Preferences.
3. Right-click HME, point to New, and then click DWORD Value.
4. Type EnableRemoteContentSharing, and then press ENTER.
5. Right-click EnableRemoteContentSharing, and then click Modify.
6. In the Value data text box, type 1, and then click OK. If you later decide to disable remote content sharing, you can repeat this procedure and change the value to 0.