I have jumped in here a little late but I may have some info for you.
the camera makes it's own folder and places the images in it. I use the same cards in my D70 and my small Canon. Neither camera see the other cameras pictures or file. they are blind to only their own. I have not formatted one of these cards to see if it wipes both files. I will have to test that. Think of the SD card just like your USB thumb drive. they are for all intent and purpose the same. you can easily put computer files on your SD card to move them to another device. You just need an I/O device. I had edited some pictures for a show that were to play in one of those large slide view Photo frames. I had to off load all of the fhotos and then load back just what I wanted to present even though they were in multiple folders on the SD card. The playing device was dumb. You can do the same thing and just load the pics you want to show on a clean card. My cousin has a scanner and he wanted to send me very old family pictures. He scanned them and sent them as a scanned image. He then photographed them with his D40 and sent them. Much improved because in shooting them they were enlarged with no grain and distortion. Try it both ways. I think you will see the difference especially if you enlarge, crop and tidy them up. I hope this helps. JB