no, you don't. Linux weenies love complaining about the lack of source code, but Windows used to have a very active modding community around it. There used to be shell replacements for Windows that allowed customising the look and feel more than Linux allows today.
The momentum dropped, just as there are much fewer themes for KDE today than there used to be in KDE3/4 times. But it's entirely possible to mod Windows into anything.
