Files won't open in iTunes

When attempting to transfer some songs from my desktop computer to my laptop through my USB stick, I haven't been able to open the songs in iTunes even though they open on my other computer. At first, there was an error message saying that I didn't have enough privileges, which I was able to fix. However, now when I try to open the files, nothing happens and no message appears. I tried opening the same files with Quicktime, and they opened just fine. Any ideas as to what might be wrong?