WD Passport 320gb Silver not recorgnized in disk management HELP!

Hello everyone,

i have a WD Passport 320gb Silver, the serial is WD3200MES-00. and i have some important files on it. It was working great but now for somereason it doesnt work. When i connect it to the computer the light shines and i hear it power on but the computer doesnt recorgnize it. It doesnt appear on my computer or device manager or disk management. I need help please to recover my files from it. Any suggestions?