Javascript Windows Framework

Sometimes I see web based software that is designed using some slick javascript windows which try to emulate the Windows desktop experience (draggable windows and a start menu).

Are there a开发者_Go百科ny free frameworks like this available?

something like ExtJs?. Here are some demos

Desktop like webpage

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I would check out jQuery UI

http://jqueryui.com/demos/dialog/

Maybe you want to have a look at http://qooxdoo.org/demo - I don't have experience with it, but it looks quite capable.