I have zipped and unzipped hundreds of music files and renumbered many of them to fit my requirements, and I can state with certainty that it does not matter if you start with 01 or 12, since the disk drive on the keyboard will only read 20 files at a time. If you have more than one file occupying one slot, when you delete the first 01, the second 01 file will magically appear. Sometimes when you zip or unzip a file with 20 songs in it, the computer will read a file from song 20 first, then continue on with all the others, in proper order. By hitting F5 on your computer's keyboard, you'll initiate an alphabetical sort and put the files back into their proper order. If you somehow fail to notice the extra file when you begin to renumber, you may end up out of sequence and the keyboard might have trouble reading the files. Just do it all over again to see if you may have introduced a little human error into the equation. BTW...when you zip up a music file, start by highlighting the last file first, then up to the first file. It will zip up in the proper order that way and unzip in the same order.