First off, I'm assuming those of you who said "I'm skinny and I want to get fat" don't really mean that. Being fat is unhealthier than begin skinny (unless severe case) - higher risk of heart attack, higher cholesterol, etc. I'm assuming you just don't want to be seen as skinny anymore - whether that means getting muscle or fat. As some people said already, you want to get "buff"
I'm in the same "predicament" Throughout high school, I was always around the 120-130# range at 5'7" - 5'10" Pretty skinny yes...I ate what I wanted, whenever I wanted, and etc. Never gained anything. Of course, I played sports daily, but I also sat on my @$$ at the computer playing games and stuff.
Now I'm 21 and about done with college. I'm still 5'10", but I'm about 155#s. The "Freshmen 15" holds true. I gained 15 pounds easy freshmen year. I'm not skinny anymore, but slim

. I've been lifting also, so I'm guessing that helped a bit also.
Summary: Weight increases with time
For those of you who want to LOSE weight, I have one question: do you do anything outside the computer? I mean, if I were "fat," I know that I'd be working out and doing stuff every day. Maybe follow Jared from Subway

But I'm also saying this having never been fat. Probably easier said than done, right?