I do have a spare monitor from my old Dell Computer, so I can hook that up in my room, but space in my room is VERY limited. Plus, I'd trip over the wires for the computer when I leave my room and I don't have a computer desk in my room too..
And here's the real kicker. Let's say that I suddenly got an idea and I want to go write it on my old computer upstairs, but my parents are there, playing their games and won't be off for a couple of hours. And that's why I want to install that video card that has TV outputs so I can hook the new computer up to my TV and use my TV as the computer's monitor.
I hope that clears everything up.