[ Thanks to linuxmint for this link. ]
“If you own a laptop with widescreen resolution such as
1280×768, 1280×800 or 1400×1050, you might have encountered that
problem. X Window shows up in 1024×768, and it doesn’t fill the
entire width of the screen. If your laptop’s graphic card is an
Intel 800 or 900 series (Intel 845G, 855G, 865G, 915G, 915GM, and
945G), there is a very easy solution to fix this…”