Yes, you can stream from Windows Media Player to your Cobblestone via a UPnP or DLNA certified controller, such as Play To. Just make sure your device and Cobblestone are all on the same wifi network. In your Media Player playlist, select “Play To” and select the Cobblestone device. Or you can right click on the song and select “Play To”.
If the speaker / device is not visible on the Windows 7 Media Player, go to Stream > More streaming options, and make sure it’s in the “Allowed” state.