Step 1:
Check if the option "Show thumbnails instead of icons" is selected on the computer.
a. Click Start, click Control Panel. (Classic View)
b. Click on the System icon.
c. Click on the advanced system settings link.
d. Under Performance, click on the Settings button.
e. In the Visual Effects tab, Check "Show thumbnails instead of icons"
f. Apply the changes, restart the computer and check if the issue persists.
Step 2:
This problem also occurs because Windows may not update the thumbnail cache.
To resolve this problem, reset the thumbnail cache. To do this, follow these steps:
a. Click Start, click All Programs, click Accessories, click System Tools, and then click Disk Cleanup.
b. If you are prompted, click My files only.
c. In the Files to delete list, click to select Thumbnails.
Note: Configure other options that you want.
d. Click OK, and then click Delete files.
e. Restart the computer and check the result.
Step 3:
If the issue persists, run sfc (system file checker) scan to scan and fix missing or corrupt system files
See
How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7
NOTE:
Sometimes non Microsoft media players may cause this issue. Disable them and check the result. Performing clean boot is like disabling non Microsoft programs.
See
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7