Ok, your computer monitor is not HD, its actually XHD or Xtreme High def. Read that on Nvidias website. Think about it, your HD tv, is generaly 720p which is 13**x720 I think. Some are 1080p, which is 1920x1080 or something. A 1080p is usually 50" or so, and 720p from 30"+ on average. My computer monitor is 20.1" The highest resolution is 1680x1050, so technicaly, thats not quite as big as a 1080p, but the pixels are packed into a much smaller area, for smaller pixels, and there for extremly clear resolution.
Understand what I am saying? So really, the resolution of a computer monitor is much higher than HD.