Ultimate Edition uses to come pre-installed with compiz and its plugins.
You need to install Compiz and check if the default plugins includes those needed to enable transparent windows, such as "Opacity, Brightness and Saturation", which controls the transparency of the windows, "Opacify" reduces/increases the opacity of the window based on the mouse over windows behavior.
See this http://askubuntu.com/a/1046/9598. And this: http://askubuntu.com/search?q=transparent&submit=search (a search in the site will provide lots of answers to your question).
I hope this give you a clue on where to begin.
BTW: I am not sure that Compiz will work fine on XFCE, when I tried Ultimate Edition it didn't, but it was the 2.8 release which used Gnome as Desktop Manager.