I have a CD that was burned on a previous version of OSX. I copied it onto my iMac, did some housecleaning, deleted some files, and then tried to burn the files onto a new CD. But I got the message that there are too many files to fit on the disk. This is funny, because the disk was originally 657 MB, and the files I wanted to burn onto a new disk totaled only 626 MB! My guess is that the newest versions of OSX (Tiger and Leopard) add so much overhead that even a smaller number of files will no longer fit. Fortunately, in my first test run with Burnz, all the files fit onto a new CD without complaint.