What did I do? New desktop environment somehow

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http://crunchbang.org – I logged out one day and logged back in and suddenly I'm running a new desktop environment. Not sure what I might have installed to do so, I was hoping someone can point me in the right direction to look for it. I believe it's gnome? I'd like to go back to openbox. Screenshot of the new desktop below. Thanks for the help! (HowTos)