PLEASE TRY THE PROGRAM BEFORE THE PURCHASE. With this program , you can use your PDA or MP3 USB Player like an iPodShuffle. You don't have to mind the limitation of SD Card free space. You can listen to different music files from those you listened yesterday. This program chooses music files at random from your PC not to duplicate with files on a SD Card or MP3 USB Player recognised as a removal disk (Hereinafter calld "device"). Then the program deletes files on the device. And then the prorams copies the choosen music files into the device until there is no vacant free space on the device or all the music files are copied. Finally the program shuts down Windows or stands-by Windows if you want. You don't have to wait for the finish of the synchronization. You have to just start the synchronization and go to bed. PC automatically turns itself off. By next morning , everything is done. You can try the program for 20 days. **This Program does not run on a Japanese computer.