Which programs have you used to try to open them? sometimes a different program will have no probs.
Do the Thumbnails view show ok? Or it may even be an 'ownership' problem and you have to take ownership of the files on the ext HDD
Nokia 8 vs Galaxy S8
Best new design books 2017: From vintage infographics to the the psychology of type
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Nokia 8 : design, caractéristiques techniques, date de sortie