GamePad Service is a C# program, which requires .NET 3.5 Client profile or later.
GamePad Service is the server program needed for NES-Controller. Once GamePad Service is started, a Windows Security Alert will pop up if your Windows Firewall is running. This is a dialog from your running Windows Firewall, whether to block the service. Make sure that the port (8003) of GamePad Service and the program itself is blocked by your firewall or any other security software.