If you want to bring the reliability of Windows to television and the picture quality of broadcast televsion to your computer (two great tastes that don't necessarilly taste good together), a TV card is all you need. There are even USB TV tuners worth checking out.
The quality? Well, your high resolution computer monitor will make apparent that which you only intellectually knew before, that TV signals are teh crap. If you watch TV on your monitor at normal computer distances (eg, 3 feet) at full size, you will need to aggressively control your gag reflex, as it will be truly terrible. If you watch the monitor/TV from the other side of the room, however, then it'll look fine, but ymmv.
Better question from me: What is your expected use? Will this be to avoid needing to buy a TV for a cramped college dorm? Or do you have another reason for it? The answers will help with suggestions.