computer won't recognize mp3 players

Hello, I'm having trouble getting my computer to recognize mp3 players. I was using a Sony, it broke, I bought an ipod and it wasn't recognized by my computer at all when I plugged it in, but because my phone and camera both work in the USB ports I thought it was the ipod and returned it. Now I've got a Creative Labs Zen and having the same problem. It's brand new, I plugged it in and it...