This article helps you if your thumbnails are not displayed in Windows File Explorer and shows you how to enable or disable thumbnails in Windows 8 or Windows 7 Explorer.
When you open the Explorer and view the images, you will see the image thumbnail in its place. These are vignettes. But if you only see the default icon, this message will help you solve the problem.
Thumbnails are not displayed
First open the disk cleaning utility and use it to delete the thumbnails. This will clear the cache of your thumbnails. Then open the Control Panel and click Open Folder Options. On the View tab, make sure that Always show icons, never disable thumbnails.