[ubuntu] Key Commands Not Working

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http://ubuntuforums.org – I think I disabled my desktop? Or the commands for it at least. Alt+F2 still works but others, especially the terminal command (CTRL+ALT+F2) do not. They used to work a while ago when I was getting Ubuntu set up to how I like it. And I've been trying over the last few days to get this to work, but it wont. Also, when I right-click on the desktop, I don't get a drop-down menu and such, and any files or folders that I had on the desktop are hidden, I can only access them through the file system. While I'm at it, can someone please explain to me the difference between the different desktop (Hardware)