NORTHAMPTON, Mass. — A Massachusetts man had pleaded not guilty to charges that he burned down his own house.Peter Zygmont pleaded not guilty Tuesday in Hampshire Superior Court to arson of a dwelling.Prosecutors say the 62-year-old set his house on fire on April 25.Court records show the Florence man's personal care attendant told police Zygmont said he was going to "torch the place" and then lit a fire in a trash can at his home.