Go to Sky Lab (Sky & Fog, click on the cloud) and there's a little button on the Sun & Moon tab, below Sun Controls, which has the caption Disable Sun Light. Uncheck it. As for the windows, make your wall positive. Remember, you have to squash the wall box in Z or X axis, so it's much thinner. My walls are X=200, Y=200 and Z=10. (they go below the floor and above the ceiling.) Declare it positive, create a small box with Z of 12 (X=40, Y=60 in my case). Position it so its center is on the center of the wall (you see the line), declare negative and then select both it and the wall, and group. you'll get a hole in the wall. The sill on the window is a squashed box, the window ... whatchamacallits are booleaned boxes done in the same way as the window hole. The glass is very thin boxes. You just have to pay a lot of attention to positioning.

-- erlik