Could someone please tell me if you are switching cards between a K100D and a K10D if the card has to be reformatted in each camera every time you switch, or if you can just format it in one camera and thereafter switch at will? Don't understand what 'formatting' technically does, just that it needs to be done. Friend bought the K10, I have the K100. Ran out of memory today while out and he offered me one of his cards to use, but then we realized it already had a few pics. on it and were afraid to either try to take pics. using the K100D or reformat for fear of messing up what was already on there. Would be good to know for the future. Thanks!