Start by turning haze and sunlight off. Create a source of light to come through the windows, such as the one you have now. You can have multiple lights slightly separated to achieve soft shadows. Refer to madmax's zenith sunlight system for that. Anyway, once that is done, make four rows of for radial lights, and group them so that it covers the whole room. Set those at about 3 or less, and turn their shadows off. Now move them around until it looks right. And last, add radial lights with shadows turned off where radiosity is needed. Might not be the proper way, but it has worked for me :D.

CLICK!