Another Problem With Sansa Clip+8Gb

[tearinghair]

I'm trying to transfer some music from itunes on to an external microSD card for my new MP3 player. I've inserted the micro card into a mini SD card and put that into a USB port, and dragged the files I wanted; but can't see what to do next. 'Burn' just opens the CD drawer. I thought perhaps it had worked anyway, but the player says 'empty' when I open the external card. However, on the computer it seems to be saying that the card has no space left, and there's a message in the manual 'only drag and drop if you have write permission for the SD card'. Added to which I can't get the microSD card out of the player....I'm flummoxed. Any help would be very welcome.