Yeah… welcome to the pain of developing perfect install/uninstall feature on Windows.
Been there, done that… And it’s really annoying to get it right.
The thing is…
For example : that data might be written to Windows registry when you define it i.e. configure your app.
When app is installed i.e by default when it
follows Windows guidelines, installation tracks only the changes what are done when app is installed. It doesn’t cover up the configuration done when app is running.
So when installation is done, it’s create a log of changes what it has done and based on that log the uninstall rolls back the changes. It doesn’t know what you have done while running the app.
This document describes folders where data is stored
One option is to check if the folder is there after uninstallation and remove it, if it makes different.
Remember… you might also delete important stuff as well…