1) WMP can share media between different computers on the same network, and with XBox 360 as well. For this to work, there’s a network sharing service that shares the library even if Media Player isn’t open, so if you use this feature you should not disable it.
To disable media sharing open up WMP, then click on the arrow under “Library” and choose the “Media Sharing” option. In the Media Sharing dialog box that opens up, uncheck both boxes. Hit OK and Yes at the prompt.
Also, stop and disable the service in Services.msc. Double click on WMP network sharing service, click on "Stop" to stop the service and change the startup type to Disabled.
2) 50-60 services are no big deal. I would say you have a pretty clean setup.