This is a proximity sensor. It detects when the laptop is in free fall mode and parks the heads of the hard disk to a safe location. The driver is used by the Drive Guard application released by HP. It allows you to protect the hard drive in case you slip it on the ground from a certain distance. It's a feature that should be used at all times. If the Drive Guard is activated, the rest should be automatic. You just need to have the driver installed and the application. It isn't used at a larger scale because user don't have any ideea what it is in the first place.
