here's what you do. go to the wardrobe room (the place where you first saw those banana-eating ghosts) and turn away from the mirror. you'll see an old man. when the old man waves his arms around and goes "whooo" (he really stinks at scaring people) turn around and vacuum him. after you do that, go to that room in the basement (i think you get a key from the old man that will let you open the door). when you enter the room, pull that switch to turn the power back on.

P.S. whenever a blackout happens, turn the volume all the way down or else you'll get the crap scared out of you by those dumb ghosts that pop up.