This is a problem caused by memory cards being increasingly used in things other than cameras. I find XP changes its behavoiur depending on mood. At the end of the day, as I have said many times before, format the card for the device you wish to use, for the device you wish to use it, as they are about as "universal" as USB ports. You will get to the goodies through persistence, but it can be a PIA. If the goods are on the card, they can be read, but it might take a bit of a different approach, than that which you expect.
Conan