Thank you so much Geethu B for putting so much thought into solving my irritating problem. Unfortunately, none of the steps worked with my system which is a Windows 7 Ultimate BUT
my son dropped in and put it all together for me fairly quickly.
1. Start Menu
2. All Programs
3. Click on Accessories
4. Click on System Tools
5. Click on Disk Clean-up
6. Delete thumbnails forcing the system to create them from your images.
7. Click on Refresh and all images, rather than icons, return to the file covers.
Did this solve your problem?
Sorry this didn't help.