The term 100% crop is somewhat of a misnomer, in that if you were to do a 100% crop on an image you would have the complete image.
What is really meant by a 100% crop is, a part of an image that is viewed at the original resolution.
On your computer you may not be able to see the complete image unless you reduce the size. If you want to show someone the original size image, there are 2 things you can do. One is show the full size image and scroll around the screen or you can do a 100% crop and just show a small part of the image at its original size.