My passport essential usb hard disk is not detecting

[sheraz83s]

I am using window Vista.I have a WD passport essential usb hard disk.it was working fine 2 days before but today when i plugged it , my computer explorer doesnot show the usb drive but it is decteted in task bar as usb drive is connected.and my pc also dont respond.I have chged my USB port and also chked in another pc but the problem persists.can anyone help me in this regard....