yes you can. only if your box is modded running a dash with an ftp client (obviousely). Read tutorials at www.xbox-scene.com.
could you run me through it as i dont understand the tutorials at xbox scene. where do i put the mp3s etc.
get xbox media center. Then make a folder of sorts in either e: or f: (you can call it anything; media, stuff, whatever). I use "media" with the subfolders "videos", "pics", and "music". Put your mp3s there. When you run xbmc, you'll have the option of searching th ehdd for your files. Once in xbmc, it's pretty explanatory. If you use xbox media player however, you'll need to edit the ini so xbmp looks in the right spot for your music.