Can I watch all my live channels on my computer if I hook up a comcast digital decoder to a USB TV tuner?

I want to be able to watch live TV on my PC and record my shows through WindowsMediaCenter, and a USB TV tuner seems like the right choice. The only problem is that the tuner only picks up analog channels. Will hooking up the Comcast decoder to the USB TV tuner let me watch all the channels I get on my regular TV?