4 GB Micro Drive.
Have you seen this? The deal is that Creative has an MP3 player with 4 gigabytes of memory. The dirty little secret is, the memory is a standard CompactFlash card type 2. There are all kinds of instructions available to gut the device. The links to the how to are in the link above. It doesn't look that hard. The modified players, the ones that have had the large drive replaced, are on eBay. If you ask me, Hitachi should lower the price of the drive and clean up. They obviously make money on the drive by selling it to Creative at a low enough price for them to wrap an MP3 player around it and sell the whole thing for less than the cost of the drive by itself. I can't find a link to the drive for sale.