Setting laptop built-in display's resolution below 1024x768?

I can't find a way to set my laptop's display below 1024x768 resolution. The Windows 8.1 'low resolution' mode (640x480) works, but that cannot really be used with multiple monitors etc. The laptop has integrated Intel and NVIDIA GPUs.

EDIT: Can't create custom resolution using Intel's drivers, because I need to use 800x600 as desktop resolution, not only on a specific application.

Solution 1:

You can't set it lower because the minimum required resolution for Windows 8.1 is 1024x768.

The minimum native resolution/color depth is 1024x768 at a depth of 32bits.

Source: Windows Hardware Certification Requirements for Client and Server Systems

Also see: http://en.wikipedia.org/wiki/Windows_8#Hardware_requirements