How do you capture all TV signal into your PC?

I do have a TV tuner card. However, that is og and only gives me a limited line-up up to 99 channels. My incoming cable carries both Internet and TV signal. How can you byp the Set Top Box and still get all the channels I have available? Are there gizmos other than a SetTopBox which you don't get from the Cable Company and which you can hook up to your PC? (I live in the US)