please help!

If you want to unlock Luigi then you don't fight Boo on the balcony, but in a secret room. You must go up the stairs to reach the Manor's second floor, then go to the door to the right, go forward and reach the red ? block in the corner go onto the platform, but don't get it, instead jump on top of it and then backflip to the platform with door straight across from it. Go through the door. jump into the Luigi painting right next to you. Go to the right door and run across the collapsing bridge (don't worry about the red coins). Once you reach the middle plattform go left and through the door. Jump to the middle (careful the floor holds a trap!) and go right and through the door. In this room you must simply use the moving platforms until you get to the platform on your left from where you start and go through the door. RUN! RUN! RUN! across the long collapsing bridge. Once you ge to the end use the moving platforms. to reach the top of the boo painting and jump into the hole. Go to the mirror and have a brief conversation with boo. Then all you have to do now is beat him, its extremely easy, just use the mirror to your advantage and punch or ground pound him until he "dies" (ghosts can never die heehee!) he will then give up the key to Luigi!

Don't worry Keith, The Kids Are Alright!