I have a large (16 mb) SD card installed on my PRS-600 e-reader. It works well. But, probably by my own clumsiness or haste, I have ended up with many books which are duplicated on both the reader and the card. Is there an easy way to remove duplicates? This probobably occurred when syncing new books to the reader, because the process just stops when its own memory is full, and doesn't automarically "overflow" onto the SD card (so I started syncing again directly to the card). It's hardly a seamless memory extension!