If I may ask, what are you trying to view (open) them with?
I've used irfanview for years, never liked the Microsoft stuff for photo's & pictures.
It could be something as simple as a file association hiccup . . Jaymoss will suss it though
edit: random thought . . years ago daughter had issues with photos transferred to windows PC from her iPhone, don't suppose you have an iPhone and it's recent photos?