Look carefully on that picture and it has a DC-in area. That mean it has to be powered to use? Instead of USB power. Not really ultra portable then is it???

I don't know any other 2.5" portable hard drive that can't be powered by USB alone, but maybe, just maybe they put that power connector on their for other uses of the hard drive, eg mp3 storage in a car attached to a car stereo.. that requires external power almost always!

I think someone is a little tired and cranky and needs to go for the afternoon nap!

"Look carefully on that picture and it has a DC-in area. That mean it has to be powered to use?"

Not necessarily - there's a better than even chance that it'll come with a 'dual headed' USB cable so it can take power from two USB ports rather than one. The DC-in socket is handy if this isn't possible for some reason.

So, it'll probably USB powered *or* mains powered at the discretion of the user.

Ignore the DC input. If you know anything about PCs, USB, and HDDs, you'd know exactly why it's there on a USB-powered HDD.

USB-powered hard drives operate outside of powered USB specifications. Even within spec, not all USB ports are powered, and I don't just mean those from an unpowered hub. Apple notebooks have long shipped with unpowered USB ports to sell their iSight firewire web cams (though they claim that it is to save batteries of something). Users of these notebooks will either need a direct power plug or a medusa cable that draws power from either A: additional ports or B: a power plug (often a USB-charger wall plug).

Just like Western Digital USB-powered 2.5" drives, the auxiliary power is optional.

It's probably a Western Digital drive, as reported here:

http://www.storagereview.com/320_gb_scorpio

The DC-in is only needed if the USB port cannot supply enough juice.

It's quite a common feature on 2.5 inch USB hard drives.

As said above, they're common place now... very few devices i have actually ship with the DC adaptor anyway, but it's there if you need it...

USB 1.0 / 1.1 are not capable of supplying the juice hence a power jack is supplied for backward compatibility.