Need help with an MP3 hook up to computer. Problems with detection. Ideas?

I had bought a Philips MP3 player months ago, but then my computer would no longer detect it, meaning I was unable to add any more music. I returned it to the store i had bought it at and they said there was a problem with the cord. They gave me a store credit and I bought a different one, a Creative Zen Microphoto. It charges through the computer and became fully charged. When I tried to add songs to it, none of my media transfer programs detected this one. I tried multiple USB cords, but noe worked. I find it hard to beleive that this one is defective as well. Could there be a problem with my computer? Also, I have a camera that also goes through the USB port, but it transfers pictures and movies fine. Treat this as a brainstorming session and give as many ideas as possible. Thank you!