DemoTools - questions and answers: screen resolution

The program says it does not work with my screen resolution of 800x600

You have probably not switched your screen resolution to 1024x768 pixels. All DemoTools software requires this screen resolution! You can not run DemoTools software at lower screen resolutions!
If you currently run a lower screen resolution (such as 800x600 pixels) you can easily switch to this somewhat higher resolution: Just right-click on a blank space of the Windows desktop, select "Properties / Settings" and then switch to the 1024x768 screen resolution. (The specific procedure might be slightly different for different versions of MS-Windows).
Please, make sure that your hardware (monitor and video board) can handle this higher screen resolution (otherwise you might end up with a blank screen).