Mp3 albums ripped in windows media player not very happy with itunes

can I place my mp3 albums that I ripped using windows media player & saved to an external hard drive directly onto an ipod using windows explorer? or must the albums be imported into a music manager like itunes? this is how I did it with my sandisk sansa, would like to know because I just got an ipod.

I tried importing my albums from my external hard drive into itunes but half if not most of the album cover art was missing, I had signed up for an account in itunes to get the art, but even after this, itunes was unable to retrieve alot of the cover art. Is it the genre of music? I have a large collection of reggae, is it not mainstream enough? even windows media player did a better job at album art, it sometimes could not find it but most of the time it did.

with the sansa, I did not need a software middleman, after ripping with windows media player & closing it, I could save a copy of my ripped albums on my external hard drive as well as in my library, so I could just drag & drop my albums straight from an mp3 music folder from my external hard drive right to my sansa mp3 player, using windows explorer, it seems this cannot be done with an ipod.