This is a Youtube video Of a window that I built for a custom house. The window weighs about 1600#. It operates the same as an old single hung window, with counterweights inside a tube frame. The tube frame weighed in at about 3000#
The window is still waiting for the hardware that will mechanically raise and lower it, but I couldn't resist shooting a quick shot of it moving. The counterweights are a little light as of the video by 60# or so, so the door is a little heavier to move up.

http://www.youtube.com/watch?v=FJOZxX2Y91c