Technically, there is no effective way of eliminating the problem. The best way to correct the problem is to replace the glass units. Obviously, seals have broken if there is condensation between the panes. If you can, drill three small 3 mm (1/8 in.) diameter holes up through the bottom of the window frame. Make sure that the holes are between the two panes of glass where the condensation has collected. Then drill another hole perpendicular to the first hole. This horizontal hole should connect with the vertical hole and lead outside-not inside. Fill the bottom of the vertical hole with putty. As the sun warms the window during the day, it will drive some of the moisture out through the holes. At night, the holes will draw in dry air. It is a tricky job, but if you are successful, it will clear up the windows without affecting their energy efficiency.