It seems that you can't ((Force Windows 8 Metro Apps to run lower resolutions below 1024x768)) ((Windows 8 Metro style apps running on low screen resolution netbooks)) ((How to enable Windows 8 Metro style apps on an older netbook)) ((Google-Suche)). If you are ok with a squeezed look, set all registry values of
Display1_DownScalingSupported to 1 and change the screen resolution to at least 1024x768.