carndonagh - you need to know why this is happening before you can resolve the problem. It usually happens because warm damp air meets a cold glass window and the moisture in the air condenses out on to the glass, due to the change in temperature. So, to resolve the problem, you either need to make the air drier (by removing the moisture - extractor fans, or preventing the moisture getting into the air - by not cooking in water or by not taking showers) OR.... by ensuring that the glass in your windows is not cold - double glazing usually sorts this one out. Finally, there are a few quick fixes but these don't really solve the problem, they just help it not appear too often - like smearing a little washing up liquid over a bathroom mirror or window glass. Your best bet is to either remove the damp warm air effectively or stop your window glass being cold !