If the thumbnail pictures are not displaying correctly, resetting the thumbnail cache will fix this (most of the time). Resetting the cache will clear it and force the automatic creation of the thumbnails as needed.
1. Click the Orb (Start Button).
2. Select All Programs.
3. Select Accessories.
4. Select System Tools.
5. Select Disk Cleanup.
7. Select your Boot drive and click OK.
8. Check the Thumbnails checkbox (make sure nothing else is checked).
9. Click OK.
10. When prompted, click the Delete Files button.