what format does this camera use on the DX card

I'm assuming you are asking about the xD memory card, a proprietary format which both Fuji and Olympus use for image capture. It is a kind of compact flash card, and according to Wikipedia, are available in capacities of: 16 MB, 32 MB, 64 MB, 128 MB, 256 MB, 512 MB, 1 GB, and 2 GB (as of 2006). Type H cards have high data rate speeds than their older sister, Type M cards, which can actually be slower than the first generation xD cards.

I'm not a big fan of camera companies that choose to create their own storage media options, as they can only be used in products made by that particular company. SONY also does this with it's memory stick technology.

A better, and much more flexible option, are cameras that use the SD card for storage as they can be used in many other brands of cameras, mp3 players and more.

So, if you change cameras, you don't have a bunch of media lying around you can't use anymore. Be advised, however, that the SD format has been upgraded to the new HCSD, HC standing for High Capacity. The HCSD can only be used in cameras designed to accept the HCSD format. But the good news is, the capacities of these new high capacity cards are reaching 8 GB!

More information on the xD card can be found on Wikipedia.