The world''s fifth-largest hard drive manufacturer, Toshiba has introduced its USB 2.0 Portable External Hard Drive with built-in capacities from 100 gigabytes to 200 gigabytes — the largest capacity in a portable, compact form factor.

Other leading hard drive makers Seagate Technology LLC and Western Digital Corp. already offer similar devices with top capacities of 160 GB.

The Toshiba drives, which are less than an inch thick and smaller than 4-by-6-inches, are designed as back up for storing computer documents, digital photos, videos or photos, and are priced from $130 for the 100 GB version and to $230 for the 200 GB model.

Hard disk drive makers are continually rushing to offer faster drives with larger storage capacities in all kinds of products as prices per gigabyte drop, making gadgets from portable MP3 players to digital video recorders and computers more capacious.

Portable external hard drives are a fledgling but growing segment and market research firm IDC forecasts that over 6 million units will be shipped out in 2008 — a 58-per cent rise from the 3.8-million shipped in 2006.