1. An image recording and playing system comprising: an image pickup unit configured to take images; an image data storing unit configured to store image data obtained from the image pickup unit; an image processing unit configured to search the image data stored in the image data storing unit and to register dissimilar images which are not similar to other image data, the dissimilar images being stored in the image data storing unit; and an image display unit configured to display the dissimilar images registered by the image processing unit, as thumbnail images, wherein the image processing unit, when there are a plurality of image data to be registered as the dissimilar images, is configured to perform calculations (a), (b) and registration (c) repeatedly until a number of the dissimilar images registered by the image processing unit reaches a designated number, the calculation (a) is calculating a similarity between one of the image data stored in the image data storing unit and each of the dissimilar images stored in the image data storing unit, the calculation (b) is calculating an accumulation of the similarities calculated by the image processing unit when each similarity is within a threshold value determined in advance, and the registration registering the one of the image data as a dissimilar image of which the accumulation of the similarities is a minimum value.