I just picked up the MPC500 w/o the owners manual. So I'm kind of lost as to how to use it. I mainly got it because you can transfer files back and forth from the computer. How do I, if at all possible, transfer a sample that I want recorded to my MPC from my computer? I've already learned how to connect through the USB but the file I dragged off my desktop is not loading in my MPC. Any help is appreciated!!