They are folders left over from deleted torrents. And they seem to have some ghost icons in them. Example a TV series shows the folder and then in the folder is ghost icon called thumbs with X next to it, but no sign of the AVI files. Another is movie and in the folder again are ghost icons with the X next to them this folder has two icons one for the old nfo and the other for the avi file.
I delete lots of torrents and there are only 4-5 folders left. I am not sure if I did something different when deleting these. But I do not see them in XP and OSX
So it does not appear to be hidden folder setting