that's a feature of your video card whenever I press ctrl+alt and one of the arrow keys the monitor goes from landscape mode to portrait or vice versa you will have to look in the settings of your monitor or the settings of your video card I have three computers and they all do the same thing but it has never been a problem for me . I used to use it on my old dell xp machine and really liked it because I could turn the monitor around it was great for reading web pages
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I would be interested to find out how many of the readers of sevenforums have this ability some video do this while others don't if you press ctrl + alt and any of the arrow keys will change the display to get it back to normal press ctrl + alt and the up arrow even my laptop will do this