When I run the slide show to view from rear of my Nikon D80, the same images come up on the
card that was just deleted.
I checked the card twice to make sure it was clean.
Was the SD card formatted? If you chose to delete all images, rather than format the card, are there some images that are marked as protected, which it would have skipped. They may show a key symbol when viewing the images on the rear screen. Also, is the card write-protected using the physical slider on the card? If so, the card would neither format nor erase, and you wouldn't be able to capture new images