Mp3/mp4 knock off help!

Hello, I have an hp pavillion amd athalon 64X2 dual core 4400+ and it has vista, i have one of those knock off mp3/mp4 players from ebay, and every time i plug it into my port to charge or to put songs on, it says unknown device and then it does nothing, i am so frustrated i have own this thing for over a year and i got to use it the first time and then poof my comp didn't recognise it anymore. Can someone please help.