Yep. Some people want to gain weight for good reasons - suited to the individual and his or her goals.
I'm sure you know how to gain weight. It's not eating more carbs or more anything - except calories. Adding fats to your diet is the easiest way (fat has more calories per gram than carbs or protein, which are equal in calories per gram).
It's been a while since I set up my profile - I've been on fitday for years and love the stuff here. But I'd suggest changing your base weight. Not your goal weight. After all, if you weigh 200 pounds, who cares if you put 350 pounds as your base weight to start and make 250 your goal weight? You're still going to see progress toward your goal, even if it looks like you're 'losing' instead of 'gaining.'