Hi Jeffrey: Usually, when we see that kind of error it is either because the folder where the file is located has too many files in it. If you have this file in a folder with other files, you may want to move it to its own folder. Otherwise, if that's not the case, you may do better to break it up. Large files--particularly audio files do tend to cause problems. Also, you may need to reformat the card to clear up the error, if moving the file doesn't help! Pamela Rader, TECHNICAL SUPPORT American Printing House For The Blind 1839 Frankfort Ave. Louisville, KY 40206 PHONE: 1-800-223-1839, Ext. 307 >>> jt.chess@xxxxxxxxxxx 08/08/07 01:05PM >>> Hi, I put all of the Harry Potter 7th book onto my Book Port as one file--a rather large file, as an MP3 from RFB&D. I was able to open and read it several times, but last night, and since then, half a dozen or so times, I get an error that says "Application file i/o error", and the file does not open. Any suggestions about how to deal with this error? BTW: The book was not in the root directory, and I still have 1600M of space left on my flash card. I am guessing the file may be too large, and it might be better to chunk it into half or a third of the book, but if there's a way around having to do this, I'd love to know. Thanks, Jeffrey