I can't get to my files, PLEASE HELP! This is costing me money!

My 500g WD My Book shows up, I can play the music from the drive when it is plugged in, but if I copy the files to my iTunes library, they won’t play after I’ve ejected the My Book (original file not located.) I tried to use the clumsy WD Smart Ware software to retieve my files, but the files that I actually wanted to retrieve were not available, what gives!?!? This is a big pain for me as I use these files as a large part of my personal income. Likewise, if I cannot easily resolve this there is certainly no way I am ever purchasing another WD drive. 

Hello there,

Have tried accessing the files from a different computer?