Do I need to do resolution size?My desktop window is smaller than the full size of my PC screen. How do I reconfigure this to make it full size again. Don't know what happened. I'm using aspire 5251 win.7-64bits 15.6"

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You probably would need to adjust the settings of your card or motherboard video chip-set. If you recently upgraded your graphics drivers that could cause an issue. How about a more detailed description of what you see (black bars on the sides), your type of operating system, internal card or on-board graphics info and type of monitor (wide screen or older 3x4 type). The more info the better. If it just occurred on its own, either your system settings changed themselves, your graphics are going bad or someone is messing with you.