What is then the best way, to find all windows roots with the current version? Have you some example code?

I haven't used filesystem, so I don't know how to do it in that. But, it is quite easy to obtain the available drive letters in Windows using the GetDriveType API call. Perhaps you can build a list separately and then match it with boost::filesystem as needed. Of course, keep in mind that any drive list is subject to change. It's certainly possible that the user may map new drives or delete existing ones after you built your list. Another consideration is that not all "roots" are drive letters. UNC paths are quite valid. There is no reasonable way to obtain a complete list there. It's somewhat possible, but would be extremely time consuming. Hope that helps some, -- Bill --