Power off USB hard disk by safely remove option.

By default in Windows 7 and Vista all usb devices remain in state of power on even after Safely Removed USB Device at the right bottom on task bar due to this When power is active state, the hdd plates are keep moving even after safely remove. so, if person unplugged his hdd from usb port then bad sector can occur due to power isstill on. This is not happen in windows XP.
To power down/off the usb device by Safely Removed option. see the registry entry in the following link or watch the above video.

http://support.microsoft.com/kb/2401954