This is allegedly the "world's first" portable HD with a 100GB capacity in 2.5".
They also have a 5,400rpm portable hard drive.
If I knew more about portable hard drives, I might be able to say something like "typical portable hard drives have low rotation speeds, typically around 2,300rpms, to keep drive noise to a minimum," but since I don't know if 5400rpms is fast or not, I really can't say anything.
And they also look almost exactly the same, besides what appears to be printed o­n the casing.

Buffalo Corporation will release both the "HD-P100U2/UC" and "HD-PHU2/UC" series portable hard drives powered by bus power beginning in the middle part of July. They are new models of the "HD-PU2" series" portable hard drives.

The "HDP100U2/UC" with a 100GB capacity will be released in the middle part of July for the price of 55,650 yen. This is the first commercialization of a 2.5" portable hard drive with this capacity. Unfortunately, the disk rotation speed has not been announced.

Beginning in the back part of July, the 5,400rpm high speed 2.5" portable HD series, the "HD-PHU2/UC" series, will be released. The lineup consists of the "HD-PH40U2/UC" with a 40GB capacity and the "HD-PH80U2/UC" with an 80GB capacity; the prices of the respective units will be 24,360 yen and 35,490 yen.

Both of the devices operate of bus power, but when this alone is not enough, users can maintain operation of the drive using the included "USB Allow Power Cable" (?) that connects the DC connector of the drive and the PC's USB port.

Supported operating systems are Windows 98, ME, 2000, and XP, as well as Mac OS 9.0.4 or above. Using the drives o­n Windows 98 requires drivers, but in the case of the HD-PHU2/UC series, the drivers are stored o­n the hard disk itself, and will automatically be read to be installed.

The body size of the units is the same; 76 x 15 x 119mm (W x D x H), and the weights are 150g. Two USB cables are included - an 80cm and 30cm.

HD-P100U2/UC


HD-PHU2/UC series


Inspired by:
http://pc.watch.impress.co.jp/docs/2004/0707/buffalo.htm

Press Release:
http://buffalo.melcoinc.co.jp/products/new/2004/026_1.html

Press Release:
http://buffalo.melcoinc.co.jp/products/new/2004/026_2.html