What do I need to connect a DirecTV box to Windows Media Center on my PC?

Can I do it in a similar fashion to the Media Share guide (http://www.directv.com/viivDownloads/pdf/DTV_quickStartGuideNewVersionFinal2.pdf) (speaking of Media Share, where can I even download the software? And would it work with an Intel Core i7 CPU and all around newer parts?), or do I HAVE to by a TV Tuner to connect it to the computer?