I have the Nav radio with the 5.1, ten speaker surround system. Recently, I got my mp3 library sorted out and tried to transfer all of my music to the hard drive. Unfortunately, it doesn't show all of the songs. It says there are 688 music files, but my computer shows 929 song files. I tried playing the music from the USB drive and it still shows only 688 songs. Looking through the owners manual it says there is a maximum of 255 folders with a hierarchy of 8 folders; each folder 18 songs or less for a maximum of 1024 files on a CD or DVD. There is no mention of this limit on the hard drive or USB flash drive. Apparently, this limit also applies to the hard drive and USB flash drive as well. Given that I have only used about 2gb of my 16gb flash drive, I'm wondering how others with extensive music libraries have gotten around this limitation, or perhaps, I'm doing something wrong. Interestingly, my other cars have no problem with this number of files.