Some people have diacritics and spaces in their usernames, which wreaks havoc for badly written programs accessing AppData or folders in the user's "home" directory, such as Documents. And there are lots of such programs.
When setting up Windows, use a short and memorable, DOS-compatible username, and then change it later (the home folder will still have the old name). You can then move indiidual Libraries (Documents, Downloads, Music, Pictures and Videos) to the root of D:\ too.