I tried to transfer a couple songs from my mac to PC earlier. I drug the tracks out of my library and onto my thumb drive. When I opened them on the windows PC, the audio files were there, along with a duplicate mpeg-4 file of each song, at 4 kb each. These were greyed out on the PC. The songs themselves like I said were there, and they were in the mpeg-4 format as well. This was a CD i personally ripped at 256kbs using the AAC encoder. Is this something itunes does on a mac that shows up if you send the files back to a pc?