Hi there, I have a mid 2009 2.8ghz model. 10.9.1 os. After I plugged an external monitor through mini port to VGA. There have been 3 desktop screens in mbp. Even I just use my mbp itself. When i use the the "swipe screen" functions, there are always 3 desktop, exactly the same layout but with different wallpapers... it is really strange. When I plug the external monitor, then these 3 desktop screens move to external monitor as I set external one as my main desktop, and there finally only one desktop in my mbp. I try to reset SMC, restart, replug ....not change at all... Please help me, how can I get my single desktop back for my old mbp? I have to access the full-screened app after I swipe 3 desktops screens .... Thank you guys..