This is my setup:
MySky
Vista MCE
WinTV-PVR-150-MCE Tuner Card
MySky is connected to PVR via antenna cable. I can display output of MySky in WinTV in broadcasted 16:9 aspect ratio (TV1, 2 or 3 or movies) if I keep it in windowed mode but as soon as I go full screen it squashes sides to 4:3 aspect and displays black bars on sides. If I record the output of MySky it records 16:9 content in the same squashed way, 4:3 atuff looks fine though.