I have a 128GB card installed along with the 64GB on board the player, and I have music stored on both cards. Since I am on an Apple MacBook, I expected more problems than I have had. Originally, the library scan was taking really long. I actually went to the settings, and changed the "Time Out/Screen Lock" to 5 seconds. I noticed that if still scanning after screen time-out, the second you unlock the player again, everything is available.