Saving the playlist file
After you have added content to a playlist, it must be saved as a .wsx file so that the publishing point can stream the content. In File name, type the location where you want the file to be saved and specify a name for the playlist file.
The server does not use your user account to access folders and other resources; it uses the Network Service account by default. If you are saving your playlist file to a location other than %systemdrive%\WMPub and its subdirectories, make sure that the folder is shared and that the Network Service account has at least Read and Write permissions for the folder. If the Network Service account does not have permissions for a folder, the server will not be able to save to it. For more information, see About rights.