There are some games or apps (like calculators) with GUI which are very small (can be of 500KB, 700KB, etc) but has all important GUI features like button, menu, displaying image, text input, etc and can work on any Windows OS without any other requirement (like JRE, .Net Framework etc). No even dlls required to run. So I wonder which language and development tools used to develop.
I have tested many GUI frameworks with C++ but even window only (without button and logic) can generate file with 3MB.
C# and Java generate very small app but they require user to install their runtime environment. Programs like "Kega Fusion" and "Mp3-Modifier" are example of those standalone app with GUI.