Western Digital on Friday said it has started volume shipments of its 500-GB notebook hard drive, which follows by several months rival Samsung Electronics' half-terabyte drive for mobile PCs.

The WD Scorpio Blue 2.5-inch drive is less than 4/10ths of an inch high and utilizes two platters with 250 GB of storage each. WD also has started shipping a 400-GB Scorpio Blue. Both drives have a 3 GB per second transfer rate and operate at 5,400 revolutions per minute.

In shipping high-capacity drives, WD and Samsung are targeting manufacturers of entertainment notebooks, which are geared toward showing and editing storage-hungry video and pictures, as well as playing music.

"The WD Scorpio Blue 400 GB and 500 GB hard drives provide the capacity needed to maximize the latest features and functions available in today's notebook computers," Jim Morris, WD's VP and general manager of notebook storage, said in a statement.

The Scorpio Blue includes several proprietary technologies that deliver quiet operation, shock protection, and efficient power consumption, according to WD. For the latter, WD has developed what it calls IntelliSeek technology, which calculates the optimum data-seeking speeds to lower power consumption, noise and vibration. WD has a demonstration of the technology on its Web site.

The Scorpio Blue 500-GB model has a manufacturer's suggested retail price of $220. The 400-GB model has a MSRP of $190. Both come with a three-year limited warranty.

Samsung started shipping its half-terabyte Spinpoint M6 in March. The drive is the same form factor as the Scorpio Blue, but uses three platters with 167 GB of storage each. The drive also has a spindle speed of 5,400 revolutions per minute and a 3 GBps transfer rate. Both the Spinpoint and Scorpio Blue have SATA interfaces.

The Spinpoint M6 has a MSRP of $299.