I think that to download songs from your computer to a flash drive, you have to go directly from whatever files you have stored the music in rather than through the iTunes program. And are you trying to upload the songs directly from an iPod to the computer in the car? I don't know if you can upload FROM an iPod. Can you connect your computer directly to the car? (I'm assuming you have a laptop, of course.) If you can, open up the iTunes program and see if it syncs with the computer on the car. If it does, you should be able to upload whatever playlist you want into the car's computer.