Computer wont read mp3 player when connected. When i plug my mp3 player into the computer with the

Question

When i plug my mp3 player into the computer with the usb cord or w/e it lights up and says ready on the screen of the mp3 ..but it doesnt connect on the computers end...it doesnt read/load it at all when i try to synchronize music onto it from windows..it says no device detected...i only have 190 songs on it and it can hold up to 400when i go and huke it up it will not copy music on my mp3 player eventho it is connected