Windows Media Center Live TV Help

I've been trying for over a month through HP chat to resolve my problem. I can't get video in my Media Center Live TV or WinDVD Creator. I did before. I did a Full Recovery. Didn't help. When I run the Media Center set up Wizard, it finds a TV signal, but no video. And when I try to watch Live TV in Media Center, it says "Loss of Signal". No one has been able to help me. How can you tell if the TV tuner card is bad ?? I didn't think it would be that if it was able to detect a signal in both the front and back connections on the PC. I have a m1297c model HP XP Media Center. Any suggestions will be welcomed. Thanks.