Photo Gallery ran perfectly until a week ago.  Now, 99% of the thumbnails have been replaced by 'a pic of an orange marigold broken in 4 pieces' and  I cannot open any of these photos.  The message error says "Photo Gallery cannot open this photo or video.  The file may be unsupported, damaged or corrupted."  I have tried 'system restore' and many other suggestions offered such as

http://support.microsoft.com/mats/windows_photo_and_slideshow_diag/en-us

http://support.microsoft.com/mats/windows_file_and_folder_diag/

I also 'repaired' Windows Essentials.  I have set the default program to Photo Gallery.

None of these actions have corrected the problem.

Can you please help me with this problem?  Many thanks!