Hi Reeeeeally basic question (don't laugh) but I have a Mac mini running 10.7.5 as an HTPC to my tv. Recently the screen won't show the full desktop. To see the top of the desktop I have to move the mouse to the top of the screen. To see the bottom I have to move the mouse down (same for each side) It's just happened recently and I can't figure it out. I have a trust wireless mouse connected that has 2 buttons on the side. I thought it might have something to do with that but I can't figure it out I've tried restarting etc but nothing. Any ideas?