When trying to download images from an xD card used in an Olympus SP-500 UZ camera, using a card readers on my laptop and on my desktop computers (Windows XP), both computers report that the card is unformated and has no images. Three different image recovery programs reported noimages (files) on the card. Yet the second time it happened, I notced that the camera could read the card and show the images. I therefore connected the camera directly to the computer and was able to download the images from both cards.
Why are xD cards unreadable by a card reader? I know the card readers work, because I have no problem reading the xD cards used by my Fuji camera.