Hitachi reached out to storage-hungry notebook users today by announcing what it claims is the world's highest-capacity 2.5-inch mobile hard drive: the 500GB Travelstar 5K500. The increase in capacity didn't come from advancements in its storage technology though, but rather from adding a third disc platter.

As a result, Hitachi's new mobile drives are not based on the industry standard of 9.5mm thickness. They are 12.5mm thick instead - meaning they most likely won't fit in your laptop or external enclosure. But Hitachi is confident that PC makers will redesign their machines to accommodate the drive because storage is a key selling point right now, and as it turns out at least one PC maker is willing to do so. Specifically, Asus will fit Hitachi's Travelstar 5K500 HDD in its new multimedia M50 and M70 notebook PCs, the latter of which will sport a terabyte of storage in a two-drive configuration.

In addition to the 500GB drive, Hitachi will also offer the 400GB E5K500 for enterprise application featuring bulk data encryption and designed for 24/7 usage. The new drives will be available in February to OEMs for about $400.