The main problem though is the default settings are out of whack for your shadow lamp. To reset them delete your lamp and add a new one. Then just set it to spot and your defaults should be right to produce buffered shadows. Also you’ll want to connect the seams of your floor and walls cause there’s a light gap. And remove doubles too. (select all vertices/Wkey/Remove Doubles)
Show us the final render. Looks like a moody scene.