http://www.theregister.co.uk/2004/07/01/sony_hd_walkman/
The NW-HD1 is a "credit card-sized" 8.9 x 6.2 x 1.4cm unit fitted with a 20GB 1.8in hard drive. There's enough RAM on board to provide 25 minutes of skip-free playback. There's a seven-line LCD for track information and player status data.
The 20GB device, called the NW-HD1, weighs less than 4 ounces, prompting Sony to claim that it is the smallest recording device built around a 1.8-inch drive. The NW-HD1 has a USB 2.0 digital interface.
At the same time Wednesday, Sony unveiled a flash media-based Walkman with a 256 MB memory that is expected to retail for about $60.