On this video Daniel Norton from Adorama demonstrates how to easily (and inexpensively) recreate the look of a window light with one strobe, any time of day and in any environment.
In this video Notron shows how to recreate the window look in a pretty inexpensive way – all you need is a light source – a strobe or even a speelight or two should do fine. What you need to do is build a large cardboard box and put your light source inside – on the front of this box you will have your “window” which Norton made out of a scrimjim (6×3 foot) although you can probably make it out of a white thin fabric if you have no other option. It is suggested that you make the whole thing a bit higher so it will look like the light is not coming from the floor.
To fill the shadows you can use a white reflector on the other side or if you want a dramatic look – use a black fabric like Norton demonstrates in the last part of the video.