Hi dipenser, have you tried Dettox Mould and Mildew remover on the black bits. Put it on, leave it for a few minutes then wash it off. If it doesn't get it all off do it again. If you get to it before it gets too bad it usually gets rid of it. As for the condensation on the windows, the only way to stop it is to have the window open even it's only a little bit. My double glazed units have a very small vent at the top which helps stop some of the condensation. Thse can be closed if needed in very cold weather. By the way it is usually the bedroom windows that are affected by this.