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#11
If your STB output works when connected directly to your TV, then you should be able to get WMC to recognize your STB, either automatically or manually in the TV setup process. Try getting a newer better box from your cable provider.
Also check all your connections to your TV Tuner from the STB and from your video card to your display/TV. This card has multiple inputs - make sure your using the right one. Also, could just be a bad cable or connector.
http://www.hauppauge.com/pics/hvr1600mckit_board-b.jpg
WinTV-HVR-1600 Media Center Kit product description