I suppose this means that you can take the HD out of the computer and throw it o­n the ground as hard as you can, and it would be alright.
But I still wouldn't recommend it.

Hitachi Global Storage Technologies (HGST) Corporation began shipment of three models of the "Travelstar 4K40," a notebook PC 2.5" HD with increased endurance, o­n March 31st to OEMs.

Three models are available: 20GB, 30GB, and 40GB. The thickness of the drive is 9.5mm, and the rotation speed is 4,200rpm. The efficient transfer speed is 370MBit/sec. The average seek time is 12ms, and the average latency is 7.1ms. The drives have a 2MB buffer. The interface is Ultra ATA/100.

The endurance of the load/unload mechanism o­n the head has had its endurance increased to 600,000 rotations, representing twice what other HGST drives had to offer. Also, using a newly designed head actuator arm, it is more resistant to vibration and shock, and can take 300G of force while operating, or 1000G of force while not operating. HGST has said that this is the highest shock resistance in the industry for 2.5" HDs.



Inspired by:
http://pc.watch.impress.co.jp/docs/2004/0331/hgst.htm

Press Release:
http://www.hitachigst.com...

Product Information:
http://www.hitachigst.com/japanese/products/travelstar/4k40.html

Specifications (English):
http://www.hitachigst.com/hdd/travel/tr4k40.htm