Sony Computer Entertainment of Japan announced today that it has sold all 10,000 of its initial Playstation 2 Hard Drive units.
Sony only made the hard drives available on its online store and the units were expected to sell through quickly given the 3 million Playstation 2 owners in Japan. The 40 GB hard drive can be used for various functions such as downloading new levels, or creating a soundtrack for a game. They are priced around $150 US.
The early success can be called somewhat of a victory for Sony given the precedence of failure for expensive add-ons (Sega CD, Sega 32X). However, the early sales are attributed mostly to hard-core gamers, so it's not yet clear if the general population will accept the add-on.