I have a device to connect any type of hard drives to a USB port of PC, and the power supply is external and different of the PC, so the device convert a hard drive as an external USB hard drive with no parking. When I expulse the external USB hard drive, it still spinning by the external power, so how can I park before expulsing it?.
Windows vista and windows 7 write to external disks using a cache method. This will prevent the source data from being lost or damaged. Of course if you unplug the drive while it is writing then the file on the external drive will be damaged.
This newer method does not require you to stop the HD before disconnecting it. Just make sure it is not in use when you yank the cable. That being said I always use the USB stop safe remove in the bottom right corner for my USB HD. However I never use it when pulling a USB thumb drive.
Parking hard drives... Thats old school... I remember with my 386 i had a 20mb harddrive and you had to run a park command before you moved the computer or the heads would crash into the platter and destroy the drive. Those days are gone, now you can pull the drive out and shake it while its running and it should be fine. (I would not do it but it should be fine).
If you want to be really carful you can go to the control panel and device manager and uninstall the drive. That will send the stop command. The trouble is the PSU on the external drive is probablly not managed, so it will never turn off automaticly. With no signal from the sata or IDE the drive will spin up to full speed and wait for a request.