Vista was basically a massive rewrite of a bunch of components, and the devs had more hw resources at their disposal when they did it. One place I can think of

Vista was basically a massive rewrite of a bunch of components, and the devs had more hw resources at their disposal when they did it. One place I can think of taking up more disk space is all of the theme ing and icons. Imagine how many different images are included in windows, those need to be high-res for hidpi now.