Sometimes it’s nice to see what MediaCenter would look like in “Full-Screen” mode vs “Widescreen”. By default, MediaCenter will display the aspect ratio that is appropriate for your monitor or tv. So if you run a screen resolution of 1024×768 you’ll get a square “fullscreen” 4:3 display, if you run 1280×720 or 1920×1080 (HD resolutions) you’ll get “widescreen” 16:9. When you run MediaCenter in a window, as opposed to maximized, you can manually switch between these aspect ratios, and it’s really simple.
Just click the corner of the window as if you were going to resize it, and then hold the control key on your keyboard and drag the edge in or out. While it scales to size (aka “scaling”), it’ll eventually snap from one AR to the other.
When you maximize the window it’s still going to fill your display, so if you have a 4:3 display and drag MediaCenter to Widescreen it won’t letterbox the interface. Same goes for users with 16:9 or 16:10 displays, you won’t get sidebars.
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TechNuggets 
Very helpful. Thanks. My windowed AR had accidently snapped to 4:3 and couldn’t find out how to correct it . Couldn’t even find this info on the MS site!