4:3 resolutions don't scale properly on 16:9 laptops

I have an Acer Aspire 5349 laptop, using Intel HD Graphics 2000. Screen resolution is 1366x768.

However, when I try to play a 4:3 aspect ratio game (such as Diablo 2 with its 800x600 resolution), there's something wrong with the aspect ratio. Althogh the aspect ratio is maintained (black bars on the sides), the screen looks more like 5:4, rather than 4:3 aspect ratio (it's somewhat distorted horizontally).

It also happens with every 4:3 resolution I try (for example 640x480). Strangely, when I try using centered aspect ratio (1:1 pixel mapping), the game looks fine. But I don't like it, as it's rather small then. Long story short, 4:3 resolutions look too ''squarish'' on the 16:9 display, and they are squashed horizontally to a small degree.

Try it. If you have only Intel HD Graphics (without any dedicated GPU) run any 4:3 fullscreen game on your 1366x768 laptop, while maintaining aspect ratio (black bars on the sides). Doesn't look quite right, eh?