Albums ripped in windows media player show in itunes but not windows expore itunes directory on my external hard drive

I notice that albums that I originally ripped in windows media player & then dragged & dropped into my itunes library show up in itunes, but when I look at my itunes library directory on my external hard drive in windows explore, those ones ripped with windows media player do not show up, but the ones I used itunes to rip do show up in windows explore. so for example; I have artist A; ripped album 1 by artist A in windows media player, then later imported into itunes, it is viewable in itunes, but does not show up in windows explore, but album B by artist A that I ripped with itunes shows up in windows explore as well as itunes.