Originally Posted by Luscious Media

Looks like a tilt in window with the panes reversed. Check the top of the inside pane near the locks for finger holes. Put your fingers in the holes and slide them towards the center of the window to unlock it and tilt the inside pane in. Then slide the inside pane almost all the way to the bottom. Now slide the outside pane all the way to the top. Tilt the lower pane back into place so the locks snap back in. Slide the inside pane all the way down, lock the window and go to bed.

Hope that helps.