back in windows xp days yes, it's pretty much never a problem nowadays. for the past...almost two decades, actually - thumbnails get stored in user profile folder since vista. (though it is different for network folders and may still be a problem.) and desktop.ini files - you'd only ever encounter them in predefined system folders (like pictures, etc.) or if you manually customize a folder in its properties - customize tab (like changing folder "type" to one like those predefined folders or changing its icon, not the same as changing size/thumbnail size/columns/etc though, that's stored elsewhere too)