Deleted photos still showing up in Preview

Has anyone ever tried to open "Preview" by itself without clicking on an image to open it and the popup screen popsup and asks which photo you want to open, select no image and just click open? It then opens a bunch of pictures that look like every picture that has ever been on my computer even deleted photos still show up when I click the button under the red X and change the view to Contact Sheet. How do I delete the phots I no longer need from my computer since they are still somewhere on my computer and there is no way to find where the file is located?