Like on Laptops, etc with "Widescreen" LCDs.
You get this with 1024x764 on a 1280x768 Widescreen Laptop LCD; looks ugly doesn't it?
Go to the desktop.
Rightclick on desktop, select properties.
Bring up the Settings tab
Advanced
And proceed to look around in there for something that says "full screen mode" or to the extent therof. Deactivicate it; and you'll get this
The screen will now be the proper proportion