There is a couple ways to get a tv as a monitor, 1 is buy a video card with a video output.(S-Video, Digital, Component, just to name a few)
Another way is to get a VGA to component adapter http://www.digitalconnection.com/products/video/9a60.asp
would you recommend using a tv screen? because i never heard of anyone doing it, and i mean if you can get a 300 dollar tv that is big why get a monitor?