According to online sources, my monitor has a resolution of 1440 x 900, but whenever I make a custom resolution, the system says that my monitor cannot display that resolution.
I was originally using VGA, but every time I restarted the computer, it would reboot with half the screen out of view and so you'd have to change to the lowest resolution and then back to 1024x768 (any higher resulted in a blue screen, and no then no change).
I'm now using HDMI which my monitor is also compatible with, and the highest resolution I've managed to get using HDMI is 1176x664, but there are black bars on the edge of the screen and the quality is bad (as in worse than with VGA)...
GeForce GTX 560
Monitor brand: Grundig
Monitor model: GU19WDPCX (it has elegance written on it, and some other versions of that model don't, if that makes a difference).
I can list more specs if required
More about :find create correct resolution monitor
That model number comes back to a TV. Which means you are probably limited to 720. You might be able to get HDMI to work better if you play with the overscan settings but I don't have any experience with this.