In "My Computer" I can't access files from USBs, MP3 players, etc.?

I think the problem may be a lack of a certain driver. Whenever I connect an Mp3, It allows me to play the music on WMA but I can't access the files at all, so I can't transfer anything. The USB devices or MP3s are not recognized at My Computer so I can't access them from there. Someone told me to go to device manager through the control panel and delete all usb hubs so they could reinstall. This did nothing. Can someone tell me what the problem is, where I can find a driver that will fix this, or if I can access my files some other way?