Many people make the mistake of thinking their windows are leaking but come to find out  after replacing the windows it was  actually their roof leaking and have to spend more money to stop the leak. One way to make a quick evaluation on wether its the windows leaking is if you see any signs of water on the wall or ceiling right above the window. Water stains or damage above the window may mean that you have a leak in the roof or even a bad soffit. This small inspection can save you time and money since replacing your windows is costly and may not stop the leak.