First time poster and a "much to learn" Macbook Pro owner.  I have almost 300GB of music that I have compiled over the years stored on my external WD Passport for Mac HD.  When I click on a music file on the HD, it will play in iTunes but it will be erased from the HD.  I have to manually drag it back to the HD from the iTunes Music Library and even rename the file to add file details like the artist of the song.     How can I stop iTunes from removing the...