my external hard drive (WD my passport) not detected on my laptop

Hi my 500GB WD Passport is not being detected by my laptop when plugged in (by USB). A LED at the side of the external hard drive indicates that it is being powered on even though the computer shows no sign of detection (no sound indication; nothing showing up in My Computer) I can feel the drive motor start up.(the vibration). my machine's BIOS detect the drive. but I can't see it in device...