Broken USB ports?

Hi, im running XP on an advent laptop. It has four USB ports. recently i noticed that my mp3 player will only work on one of them and my external HD will only work on two of them. When connected the mp3 player to one of the ports nothing happens but when connectin to the other two that it will not function with it says that the device is not recognized and that there may be no drivers installed for the device. I would however eliminate a problem due to software as it works perfectly fine on one of the ports. My external HD will work with two of the ports, when connected to one of the others it is apparent that it is recieving power from the port as the lights come on on the drive, however the drive is either not recognized or not registered at all. Just wandering if anyone can shed any light on my problem. Thanks in anticipation!!